whetstone

He approved of Parpon, and never lost a chance of sharpening his humour on the dwarf's impish whetstone of a tongue.

Behind him, each of the natives had laid his stabbing-knife, skinning-knife, and whetstone.

It's colder'n a blue whetstone, so put on all the clothes you've got.

It is a profession which uses the conscience as a whetstone upon which to sharpen the intellect.

His firm and close-grained mind was a sort of whetstone on which my father sharpened his wits at this weekly setting.