An Etymological Dictionary of the German Language/bähen

by Friedrich Kluge

bähen, vb., ‘to warm by poultices, foment, toast (bread),’ from the equiv. MidHG. bœn, bœjen, OHG. bâjan, bâan. The Teut. root is bê, from pre-Teut. bhê, to which ba- of the OTeut. words for Bad is related by gradation. The orig. sense of the primit. stem bhê, by gradation bha, was probably ‘to make warm by washing, bathing.’