Slug
late Middle English (in the sense ‘sluggard’): probably of Scandinavian origin; compare with Norwegian dialect slugg ‘large heavy body’. Sense 1 dates from the early 18th century.
wiktionary
Originally referred to a slow, lazy person, from Middle English slugge, probably of Old Norse origin; compare dialectal Norwegian sluggje(“heavy, slow person”). Compare also Dutch slak(“snail, slug”).
Uncertain. Perhaps somehow from Proto-Germanic *slagiz(“a blow, strike”). If so, then ultimately cognate with German Schlag(“blow, hit”) and Dutch slag(“blow, strike”).
etymonline
slug (n.1)
"shell-less land snail," 1704, originally "lazy person" (early 15c.); related to sluggard.
slug (n.2)
"lead bit," 1620s, perhaps a special use of slug (n.1), perhaps on some supposed resemblance. Meaning "token or counterfeit coin" first recorded 1881; meaning "strong drink" first recorded 1756, perhaps from slang fire a slug "take a drink," though it also may be related to Irish slog "swallow." Journalism sense is from 1925, originally a short guideline for copy editors at the head of a story.
slug (n.3)
"a hard blow," 1830, dialectal, of uncertain origin; perhaps related to slaughter or perhaps a secondary form of slay.
slug (v.)
"deliver a hard blow with the fist," 1862, from slug (n.3). Related: Slugged; slugging. Slugging-match is from 1878.
