minnow n.

small freshwater fish, early 15c., meneu, probably related to Old English myne, earlier *mynwe, a name for some kind of fish, from Proto-Germanic *muniwon (source also of Middle Low German möne, Dutch meun, Old High German muniwa, German Münne), a word of unknown origin, perhaps from PIE *men- "small." Perhaps influenced in Middle English by French menu "small." In the U.S., applied to various fishes of small size.