1610s, "lever (on an organ) worked by foot," from French pédale "feet, trick with the feet," from Italian pedale "treadle, pedal," from Late Latin pedale "(thing) of the foot," neuter of Latin pedalis "of the foot," from pes (genitive pedis) "foot," which is from the PIE root *ped- "foot."
The word was extended by 1789 to any part of a machine or apparatus which transmits power from the foot of the operator. Pedal steel guitar (so called from the pedals which change the tension of the strings) is attested by 1959. Pedal-pushers "type of women's trousers suitable for bicycling" is from 1944 (pedal-pusher "a bicyclist" is from 1934).
When college girls took to riding bicycles in slacks, they first rolled up one trouser leg, then rolled up both. This whimsy has now produced a trim variety of long shorts, called "pedal pushers." [Life magazine, Aug. 28, 1944]