An Etymological Dictionary of the German Language/Annotated/bähen

by Friedrich Kluge

bähen, verb, ‘to warm by poultices, foment, toast (bread),’ from the equivalent Middle High German bœn, bœjen, Old High German bâjan, bâan. The Teutonic root is bê, from pre-Teutonic bhê, to which ba- of the Old Teutonic words for Bad is related by gradation. The original sense of the primitive stem bhê, by gradation bha, was probably ‘to make warm by washing, bathing.’