An Etymological Dictionary of the German Language/Annotated/dumm
dumm, adjective, ‘stupid, silly,’ from Middle High German tum (genitive, -mmes), tump (genitive -bes), ‘stupid, foolish, weak in understanding, dumb,’ Old High German tumb. In Gothic dumbs, Old Icelandic dumbr the adjective is equivalent to Anglo-Saxon and English dumb; the Old High German word, in addition to the meanings of Middle High German, has likewise the signification ‘deaf,’ which also belongs to dumm in early Modern High German. ‘Dull in sense and intellect’ may be the primary sense of the adjective, which has not yet been found in the non-Teutonic languages; stumm too has a peculiar history; see schmecken, hell. Words expressing the perceptions of one sense are often transferred to those of another. Hence Gothic dumbs, ‘dumb,’ Old High German tumb, ‘deaf, dumb,’ may possibly be allied to Greek τυφλός, ‘blind’ (root dhubh; τυφ by the well-known rule for θυφ). This conjectural etymology is quite as uncertain as that offered under Dieb.