"pertaining to slugs," 1650s, with -ous + Latin limax (genitive limacis) "snail, slug," from Greek leimax, from PIE root *(s)lei- "slime" (see slime (n.)). The Greek word is cognate with Russian slimák "snail," Lithuanian slíekas "earthworm," and the first element in Old English slaw-wyrm "slow-worm."