An Etymological Dictionary of the German Language/Buhle
Buhle, m., ‘lover, paramour,’ from MidHG. buole, m., ‘near relative, lover, sweetheart’; likewise MidHG. buole, f., ‘lady-love’ (OHG. Buolo, m., as a masculine name only); the implied correspondences in the cognate Teut. dialects are not recorded. It is scarcely disputable, however, that a primit. Germ. word lies at the base of Buhle. Since Bube in Up Germ. dialects signifies ‘lover’ also, it is perhaps connected with Buhle, which may a term of endearment formed from it.