merwife

The story

1. Proto-Germanic · inherited from*mariwībą“mermaid, siren”
2. Proto-West Germanic · inherited from*mariwīb
3. Old English · inherited frommerewīf“water witch, mermaid”
4. English todaymerwife

From Old English merewīf (“water witch, mermaid”), potentially to an earlier Proto-West Germanic *mariwīb, from Proto-Germanic *mariwībą (“mermaid, siren”). By surface analysis, mer- + wife. Cognate with Old High German meriwīb. The construction varries regionally for the same basic folklore in Europe. Compare Old Swedish marnunna (literally “mer-nun”), Swedish havsfru (literally “sea-wife”), English mermaid (literally “mer-maiden”).