"pertaining to fat, fatty," 1743, from Modern Latin adiposus "fatty," from Latin adipem (nominative adeps, genitive adipis) "soft fat of animals, fat, lard," which is said to be from Greek aleipha "unguent, fat, anything used for smearing," a word related to lipos "grease, fat," from PIE root *leip- "to stick, adhere," also used to form words for "fat." With change of -l- to -d- "prob. due to Umbrian influence" [Klein]. But it could as well be a native Italic formation from the same roots, *ad-leip-a "sticking onto."
