1590s, "compact, trim" (of a ship), especially "protected from the weather," perhaps from a Scandinavian source such as 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).
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<a href="https://www.etymonline.com/word/snuggle">Etymology of snuggle by etymonline</a>
Harper, D. (n.d.). Etymology of snuggle. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/snuggle