PLY (2)

Ply, v. i. 1. 1. To bend; to yield.
It would rather burst atwo than plye. Chaucer. The willow plied, and gave way to the gust. L'Estrange. 2. 2. To act, go, or work diligently and steadily; especially, to do something by repeated actions; to go back and forth; as, a steamer plies between certain ports.
Ere half these authors be read (which will soon be with plying hard and daily). Milton. He was forced to ply in the streets as a porter. Addison. The heavy hammers and mallets plied. Longfellow. 3. 3. (Naut.) To work to windward; to beat.