The Etymology of Sloths’ Names

The etymology of Sloths’ Names

Etymology is the study of words, particularly, the history of words. Thus, the etymology of a word is its origin and developmental history. So what is the etymology of the word sloth? And how does its scientific and common name share the same meaning?

An unfair name

When Europeans first encountered sloths, it is fair to say they were not impressed. Sloths are the only animal whose common name is derived from one of the seven deadly sins.

In 1749 the French Naturalist Georges-Lois Leclerc de Buffon described them thus:

“Slowness, habitual pain, and stupidity are the results of this strange and bungled conformation. These sloths are the lowest form of existence. One more defect would have made their lives impossible.”


Buffon 1707-1788.jpg
Undoubtly, Comte Buffon was a quite fancy man. Portrait by François-Hubert Drouais – Musée Buffon à Montbard


Sometimes common names are not always scientifically accurate, so let’s take a look at the history of “sloth”.

Slow and lazy across all vernacular languages

It’ll come as no surprise to anyone that the word sloth has many negative connotations. Through its etymology, this unconstructive word goes back to its earliest meanings in Old English(slǣwþ), which translates as “lazy” or “inert”.


sloth illustration buffon
The illustration of a sloth from the Comte de Buffon’s ‘Histoire Naturelle’


In most languages the name for sloth (the animal) is equivalent to some form of sloth (the attribute): slowness, lateness, indolence, or laziness–leading to centuries of stereotyping sloths as creatures lacking in competence and motivation.

The first European documented naming of our furry friends comes from the Portuguese “preguiça” which in turn comes from the Latin word “pigritia”, meaning “slow”. We can still hear echoes of this in the modern Spanish name for these animals: “perezoso”.

How do species come by their scientific names?

Carl Linnaeus is known as the father of modern taxonomy. Taxonomy is the scientific study of naming, defining, and classifying groups of biological organisms. The word finds its roots in the Greek language τάξιςtaxis (meaning ‘order’, ‘arrangement’) and νόμοςnomos (‘law’ or ‘science’). Linnaeus was the first to implement binomial nomenclature or the “two-term naming system” by which we refer to all fauna and flora today.

Carl von Linné.jpg
Carl Von Linné by Aleksandr Roslin – Nationalmuseum press photo

The first part of a scientific name identifies the genus, which is a taxonomic category that ranks above species and below family (e.g. Bradypus). It is always capitalized. The second part of a scientific name identifies the species (e.g. variegatus) and is usually descriptive and always lower case.

The rules Carl Linnaeus implemented are rigid, strict, and drummed into biologists at the very beginning of their studies. Done right, these names are very useful since they can describe several features of the species in only two words. 

In this list, you can find the Greek and Latin words most commonly used in systematic names, along with their English translation. Take a look–we bet you’ll find some interesting examples!

The name Xenarthra

Sloths and their cousins, the anteaters and armadillos, are part of an ancient Superorder called Xenarthra. Xenarthra” literally means “strange joints”. The name has its etymological roots in ancient Greek, with xénos (ξένος) meaning  “foreign” or “alien” and arthron (ἄρθρον) meaning “joint”.

armadillo and anteater


Most mammals have very similar skeletons, with the same number of bones in the same places, stretched or shrunk or shaped accordingly. Xenarthrans, however, have somewhat strange skeletons compared to other mammals, and each family member has a slightly different joint adaptation. Sloths, for example, have an anomalous number of cervical vertebrae and surprisingly numerous ribs.


Bradypus trydactylus skeleton

The superorder Xenarthra is split into two different orders – Pilosa and Cingulata. In biological classification, orders, like superorders, are capitalized.

The order Pilosa includes both anteaters and sloths, and translates to “the ones with fur”. Cingulata comes from Latin word for belt Cingula and this order includes armadillos as well as the extinct glyptodonts and pampatheres.

Sloth Genus

The genus (remember, a genus ranks below order and above species, and is the first name in the scientific binomial system) names for the two- and three-fingered sloths (the animal) are synonyms for the word sloth (the attribute).

The Greek words for “lame” and “slow” combined with the Greek word for “foot” (“pódi”) give us Choloepus and Bradypus–translating to “lame footed” and “slow footed” respectively.

Fingers (not toes)

Two sloth species–Choloepus didactylus (Linnaeus two-finger sloth) and Bradypus tridactylus (Pale-throated sloth)–take their Latin species names from their most distinctive features: their fingers.


Choloepus didactylus Bradypus tridactylus-min


Dactylus” comes from the Greek word meaning “finger” or “digit”. The three syllables of the word “dactylus” are thought to each represent a phalangeal bone in a finger: da-cty-lus.

Didactlylus translates to “two-finger” and tridactylus translates to “three-finger”–highly appropriate names for the most distinguishing feature of each sloth species.


The three-fingered sloths

Bradypus variegatus: Brown-throated three-fingered sloth

Variegatus shares its root with other words we still use today–variable, variegate, and all its variations–meaning made of different sorts and colors. Variegate is a common description and is used scientifically for many different animals and plants whose colors are mottled and changeable. One example is the brown-throated three-fingered sloths, who have pale to dark grey fur as well as distinctive speculums on their backs.


Bradypus variegatus
The different shades and colors of Bradypus variegatus

Bradypus pygmaeus: Pygmy sloths

The word “pigmei” was first coined as we know it by the ancient Greek philosophers Homer and Herodotus to describe people from northern Africa and Asia. However, the etymology of this word reaches even further back and was originally used as a unit of measurement. “Pygmē” was a “cubit” or “fist” (“pyx” in Latin, think “pixi”) which measured around 34 centimeters (13.5 inches) and was commonly represented as the distance from one’s elbow to one’s knuckle.


Pygmy three-fingered sloth Bradypus pygmaeus . Isla Escudo de Veraguas, Panama. Photo: Suzi Eszterhas

Bradypus torquatus: Pale-throated three-fingered sloth

The Latin word “torqueō” means “to twist and bend”. It gives us the word “torque” as in torque wrench, and also the word “torture”. With their nine cervical vertebrae (two more than most mammals), three-fingered sloths have the ability to turn their heads a full 270°, which probably seemed quite torturous to early biologists, and likely had some influence on the sloth’s Latin species name.


maned sloth brazil
A Maned Sloth turning its head. Photo: Suzi Eszterhas

Two-fingered sloth names

It is a very human thing to name things after ourselves, even when what we are naming is another species of animal.

Choloepus didactylus, literally “lame-foot” “two-fingered”, is the scientific name of the Linnaeus two-fingered sloth, named after the very same Carl Linnaeus mentioned above; the prominent figure of natural biology and father of taxonomy.


Linnaeus two-fingered sloth
Linnaeus two-fingered sloth


The other species of two-fingered sloth is named for Karl Hoffmann, a German naturalist who was the first person to give Choloepus hoffmanni, or Hoffmann’s two-fingered sloth, its taxonomic classification. (He also named three bird species, a snake, and a millipede after himself.)

two fingered


It is wrong to say that these men were the first to “discover” these animals, as generations of people indigenous to the areas had been observing these animals long before European biologists came along to give them their scientific names, but etymology is literally the “history” of words, a word which itself means a written record of the past. Cultures whose oral or written history was lost or destroyed lost their etymology along with their history.

Giant sloths and ground sloths

The most famous giant sloths are of the genus called Megatherium, from the ancient Greek words “mega” (big) and “therio” (beast)–a perfect name for a sloth the size of an elephant.

giant sloth


Another famous genus is called Mylodon, from Greek “mule” meaning “mill, molar” and “odous or odont” meaning “tooth”.

Megalonyx is yet another genus of giant ground sloths, this one from “mega” again and the Greek word “ὄνυξ”, which means “claw”. Megalonyx is therefore the genus of “big claw”. “ὄνυξ” also became the Latin word “onyx”, which came directly to English as the gemstone of the same name, representing the fingernail-like looks of some of the lighter stones.

Three-toed sloths? Or Three-fingered sloths?

The two species of sloths are commonly called either three-TOED or two-TOED sloths, however, this naming is not precise. Technically, all sloths have three toes on their hind feet.–the distinctive numbers of digits are on their hands, therefore, the proper name should be three-FINGERED and two-FINGERED sloths.

It’s likely that the alliteration of the words “two” and “three” with the suffix “toed” keeps this name in circulation, but if you want to sound like a scientist without having to learn Latin and Greek, you can start by telling your friends: technically, there is no such animal as a two-toed sloth.

Do Sloths drink water?

Do Sloths drink water?

You have probably never seen a sloth drinking water. In fact, very few people have! As a result, it has been assumed for centuries that sloths get all of the water they need from the fresh rainforest leaves that they eat, and few documented observations exist of either of the two sloth genera drinking in the wild.

We photographed a male brown‐throated sloth (Bradypus variegatus) lapping water from the surface of a river in Costa Rica. Our latest work ‘Sloths hanging out for a drink’ has just been published in the scientific journal Frontiers in Ecology and the Environment.



This sighting prompts many additional questions. For example, how widespread is drinking behavior and how frequently does it occur? Methods used to assess water retention in wild sloths suggest that this behavior seldom occurs, so drinking is likely a method of maintaining osmotic balance when faced with extreme ambient temperatures, low precipitation, or increased consumption of mature (ie drier) leaves.



If freshwater access is indeed important, there are further implications relating to the captive husbandry of sloths in zoos and rescue centers (where they often face drier climes, typically don’t have access to water, and have a very low survival rate), and for conservation, especially after habitat fragmentation, where changes in land use can restrict water access (eg irrigation diverting stable water sources, roads that are difficult for strictly arboreal animals to cross).

Moving forward, the predicted trend toward a hotter, drier climate for Central and South American rainforests may negatively impact the sloths’ potentially delicate water balance, particularly in view of their limited energy budget and inability to travel long distances. If all sloths need a drink from time to time to stay healthy, it’s important to make sure they can get one.


drinking water


-Dr. Rebecca Cliffe