The Collaborative International Dictionary of English v.0.48:

Cammock \Cam"mock\, n. [AS. cammoc.] (Bot.)
   A plant having long hard, crooked roots, the Ononis
   spinosa; -- called also rest-harrow. The Scandix
   Pecten-Veneris is also called cammock.
   [1913 Webster] Camomile