pinion

pinion \PIN-yuhn\, noun:

1. Machinery. A. a gear with a small number of teeth, especially one engaging with a rack or larger gear. B. a shaft or spindle cut with teeth engaging with a gear.
2. Metalworking. a gear driving a roll in a rolling mill.

"Replace the crank pinion," Slade called over his shoulder, "and put it on the USC account."
-- Richard Walter, Escape from Film School, 1999

He was like a wondrous machine, the minister marveled, muscle and bone in place of crank and pinion.
-- Karl Iagnemma, The Expeditions, 2007

Pinion comes from the classical Latin pectin meaning "comb." It came to English in the mid-1600s.