barm

From Middle English barm, barme, berm, bearm, from Old English bearm (“lap; bosom”), from Proto-West Germanic barm, from Proto-Germanic barmaz (“lap; bosom”), from Proto-Indo-European *bʰer- (“to bear”). Cognate with German Barm (“lap; bosom”).

From Middle English berme, berm, from Old English beorma, from Proto-West Germanic *bermō (“yeast; barm”); related to the dialectal Low German Bärm (“yeast”), from Middle Low German barm, berm. The cake sense is possibly a shortened form of barmcake, which would be made with yeast as described in that sense, or possibly it is from the Irish bairín breac, a type of bread.

From Middle English bermen, from the noun (see above).