knurl

A knob, knot, or other small protuberance.

One of a series of small ridges or grooves on the surface or edge of a metal object, such as a thumbscrew, to aid in gripping.

To provide with knurls; mill.

A knot; a hard substance; a nodule of stone; a protuberance in the bark of a tree.

A deformed dwarf; a humpback.