1590s, "compact, trim" (of a ship), especially "protected from the weather," perhaps from a Scandinavian source, cf. Old Norse snoggr "short-haired," Old Swedish snygg, Old Danish snøg "neat, tidy," perhaps from PIE *kes- (1) "to scratch" (see xyster). Sense of "in a state of ease or comfort" first recorded 1620s. Meaning "fit closely" is first found 1838. Expression snug as a bug in a rug attested by 1769; earlier snug as a bee in a box (1706).