An Etymological Dictionary of the German Language/Annotated/Fastnacht

by Friedrich Kluge

Fastnacht, feminine, ‘Shrove Tuesday,’ from Middle High German vasenaht, ‘eve of the first day of Lent.’ According to the Old Teutonic computation of time (compare Abend) the evening and night were counted as part of the following day (thus in Anglo-Saxon frîgeœ̂fen, ‘Thursday evening,’ frîgeniht, ‘Thursday night’). The meaning given above did not belong to the word originally. The first part of the compound is an old verb faseln, ‘to play the fool’; the form Fastnacht may have been introduced by the priests.