nocturnal Madagascar mammal, 1795, given this sense by Linnaeus, from Latin lemures (plural, singular lemurum) "evil spirits of the dead" in Roman mythology, a word of uncertain origin. De Vaan finds it likely that it and Greek lamia are borrowings of a non-Indo-European (perhaps Anatolian/Etruscan) word for malevolent spirits.
The oldest usage of "lemur" for a primate that we are aware of is in Linnaeus's catalog of the Museum of King Adolf Frederick of Sweden (Tattersall, 1982); .... In this work, he explained his use of the name "lemur" thus: "Lemures dixi hos, quod noctu imprimis obambulant, hominibus quodanmodo similes, & lento passu vagantur [I call them lemurs, because they go around mainly by night, in a certain way similar to humans, and roam with a slow pace]" [Dunkel, Alexander R., et al., "Giant rabbits, marmosets, and British comedies: etymology of lemur names, part 1," in "Lemur News," vol. xvi, 2011-2012, p.65]