An Etymological Dictionary of the German Language/bei
bei, prep. and adv., ‘by, near, about’; the accented form of the unaccented prefix be; the Goth used in both cases bĭ; the Englishman makes a distinction like the German; AS. bî, E. by, but be as a prefix. OHG. bî and bi- (comp. also Beichte, Beispiel). In Goth. bĭ means ‘around, near’; hence its kinship with Gr. ἀμφί, Lat. ambi- is probable; the loss of the first syllable am- also occurs in the OTeut. word for beide; the base is probably ambhi-; comp. also um.