An Etymological Dictionary of the German Language/Annotated/bieder
bieder, adjective, ‘staunch, honest,’ from Middle High German bíderbi, Old High German biderbi, ‘serviceable, useful,’ then ‘brave, gallant’ (compare besser for a similar of idea); literally ‘suitable to one's need or purpose,’ for the adjective is a compound of the stem of dürfen, ‘to he in need of,’ and the prefix bi, which has retained its earlier accent without being replaced, as it usually is, by bî. The Gothic form was perhaps *bíþarbs; further, the adjective is identical with derb.