An Etymological Dictionary of the German Language/Annotated/Geck

Geck, masculine, ‘fool, fop, buffoon,’ originally Middle German (and Low German), in which gëc, gëcke, masculine, ‘silly fellow, fool, droll fellow,’ occurs even in the Middle High German period; not allied to Middle High German giege, ‘fool,’ mentioned under gaufeln. Compare Dutch gek, masculine, Danish gjœk, ‘fool,’ Icelandic gikkr, ‘crafty, coarse person.’