An Etymological Dictionary of the German Language/bitter
bitter, adj., ‘bitter,’ from the equiv. MidHG. bitter, OHG. bittar. This t, since it comes before r, represents the t common to the Teut. cognates; before r the permutation of t to ȥ, tz does not take place (comp. Eiter, lauter, zittern); OLG. bittar, AS. bittor, biter, E. and Du. bitter; hence we should have expected Goth. *bĭtrs, for which a form with a remarkable ái, baitrs, ‘bitter,’ occurs. The word is undoubtedly cognate with beißen (root bit, inf. bîtan); the adj. properly signifies ‘pricking, sharp,’ being now, like beißen, restricted to the taste. For other cognates comp. beißen.