An Etymological Dictionary of the German Language/Annotated/bitter
bitter, adjective, ‘bitter,’ from the equivalent Middle High German bitter, Old High German bittar. This t, since it comes before r, represents the t common to the Teutonic cognates; before r the permutation of t to ȥ, tz does not take place (compare Eiter, lauter, zittern); Old Low German bittar, Anglo-Saxon bittor, biter, English and Dutch bitter; hence we should have expected Gothic *bĭtrs, for which a form with a remarkable ái, baitrs, ‘bitter,’ occurs. The word is undoubtedly cognate with beißen (root bit, infinitive bîtan); the adjective properly signifies ‘pricking, sharp,’ being now, like beißen, restricted to the taste. For other cognates compare beißen.