What is a tooth, cam, or catch for imparting or receiving motion, as on a gear wheel, or a lifter or wiper on a shaft; originally, a separate piece of wood set in a mortise in the face of a wheel called?

cog — (Mech.) A tooth, cam, or catch for imparting or receiving motion, as on a gear wheel, or a lifter or wiper on a shaft; originally, a separate piece of wood set in a mortise in the face of a wheel. (Webster's 1913.)

Sources