An Etymological Dictionary of the German Language/stolz
stolz, adj., ‘proud, haughty, arrogant,’ from MidHG., late OHG. stolz, ‘foolish, arrogant, stately, splendid, magnificent, high-minded.’ The assumption that the word was borrowed from Lat. stultus, ‘foolish,’ whence Ital. stolto, ‘foolish,’ does not meet the case, for OFr. estout, ‘arrogant, bold,’ is borrowed from pre-HG. *stolto-, the meaning of which is scarcely explicable by Lat. stultus, only MidHG. stolz, ‘foolish,’ shows the influence of the Lat. and Ital. signification. Teut. *stolto is considered to be cognate with Stelze. E. stout seems to be borrowed from MidDu. stout (for stolt), with a different development in meaning. — Stolz, m., ‘pride,’ is a subst. lately formed from the adj.