Slug comes from Middle English slugge ('a lazy person'), probably of Scandinavian origin, akin to Norwegian dialect slugg ('a heavy body'); the mollusc and 'lump of metal' senses derive from this notion of a sluggish, heavy mass. The historical chain includes Old Norse slugg. Older glosses in the chain include "a lazy person", "a heavy body", and "lump of metal", which help explain the semantic range of the modern word. Morphologically, slug is best read as borrowing, yielding an English noun and verb shaped by both form history and later usage. In current English it functions as a noun and verb, with the sense "a slimy shell-less mollusk; also a hard blow or a bullet". English derivatives include sluggish, sluggard, and slugger; related forms include sluggard. The result is an English noun and verb whose etymology preserves the older forms while supporting the word's specialized modern meaning.