fetlock

Etymology

From Middle English fitlokes, feetlakkes pl, equivalent to foot + lock (“tuft of hair”). Cognate with Dutch vitlok, vittelokke, vitslok, German Fissloch, Fisloch, Fislach (“fetlock; pastern”).

noun

1. A joint of the horse's leg below the knee or hock and above the hoof.
   It was the better part of a mile wide, but save for some fathoms in the middle, where the Sker current ran, it was no deeper even at flood than a horse's fetlocks. 1902, John Buchan, The Outgoing of the Tide
2. The tuft of hair that grows at this joint.