An Etymological Dictionary of the German Language/blühen
blühen, vb., ‘to bloom, flower,’ from the equiv. MidHG. blüen, blüejen, OHG. bluojan; a wk. vb., which, however, judging by AS. blôwan (E. to blow), ‘to bloom,’ was formerly strong; Goth. *blôjan. the Teut. stem blô- has a wide ramification in particular dialects; the primary sense is ‘to bloom.’ It is further apparent in many words for Blatt (‘leaf’) and Blume (‘flower’); see the following word, where the non-Teut. cognates are discussed.