word-forming element used from 19c. and meaning "fine, small, thin, delicate," from Greek leptos "small, slight, slender, delicate" (see lepton).
Entries linking to lepto-
lepton n.
elementary particle of small mass, 1948, from Greek leptos "small, slight, slender, delicate, subtle," literally "peeled," or "threshed out" (from lepein "to peel," from PIE *lep- (1), a root which yields words for "peel" as well as "small shaving, scale (of a fish)," hence used of things fine, delicate, or weak; see leper) + -on. In Greek it was the name of a small coin, from neuter of leptos. Related: Leptonic.