breast (n.) Look up breast at Dictionary.com
Old English breost "breast, bosom; mind, thought, disposition," from Proto-Germanic *breustam "breast" (cognates: Old Saxon briost, Old Frisian briast, Old Norse brjost, Dutch borst, German brust, Gothic brusts), perhaps literally "swelling" and from PIE root *bhreus- "to swell, sprout" (cognates: Middle Irish bruasach "having a broad, strong chest," Old Irish bruinne "breast"). The spelling conforms to the Scottish and northern England dialectal pronunciation. Figurative sense of "seat of the emotions" was in Old English.