It displaced earlier sleuthe, from Old English slæwþ, Kentish slewð, "sloth, indolence." The modern form might also be the old word conformed to the vowel in the adjective. The modern sense of "slowness, tardiness" is attested from mid-14c. As one of the deadly sins, it translates Latin accidia. A sloth-salve (c. 1400) was a (figurative) remedy for indolence.
The slow-moving South American mammal was first so called 1610s, a translation of Portuguese preguiça "slowness, slothfulness," from Latin pigritia "laziness" (compare Spanish perezosa "slothful," also "the sloth").
updated on January 12, 2023