knap

1. the crest of a hill.

   a pathway winding around the knap of a green hill

Old English cnæpp, cnæp .

1. shape (a piece of stone, typically flint) by striking it, so as to make a tool or weapon or a flat-faced stone for building walls.

   buildings made of knapped flint

late Middle English (in the sense ‘to knock, rap’): imitative; compare with Dutch and German knappen ‘crack, crackle’.