An Etymological Dictionary of the German Language/Rüpel

by Friedrich Kluge

Rüpel, m., ‘coarse fellow, lubber,’ prop. a Bav. abbreviation of Ruprecht (hence Rüpel and Rüppel as surnames); for a similar use of proper names comp. Metze. Probably the meaning of Rüpel was occasioned by Knecht Ruprecht, ‘Knight Robert’ (bugbear in nursery tales), in whose character maskers disported themselves in a rude and coarse manner.