From Longman Dictionary of Contemporary Englishtreadletread‧le /ˈtredl/ noun [countable] Ta flat piece of metal or wood that you move with your foot to turn a wheel in a machine
Examples from the Corpus
treadle• The women of San Pablo had returned to home-work, making dolls' dresses on treadle operated machines.• Will they really want treadle or dread?Origin treadle Old English tredel, from tredan; → TREAD1 