Middle English word bosum comes from Proto-Indo-European *bʰōw-, and later Proto-Germanic *bōsmaz ((anatomy) bosom.)

Detailed word origin of bosum

Dictionary entry	Language	Definition
*bʰōw-	Proto-Indo-European (ine-pro)	to swell, inflate, to blow, swell , to dwell
*bōsmaz	Proto-Germanic (gem-pro)	(anatomy) bosom.
bōsm	Old English (ang)
bosom	Middle English (enm)

Words with the same origin as bosum