Meaning

noun the joint between the cannon bone and the pastern

noun projection behind and above a horse's hoof

originFrom Middle English fitlokes, feetlakkes pl, taken to be foot + lock (“tuft of hair”) but actually a misdivision of Old English -oc. Cognate with Middle Low German fitlok, fitlock (“fetlock”), Dutch vitlok, vittelokke, vitslok, German Fissloch, Fisloch, Fislach (“fetlock; pastern”).

Etymology from Wiktionary, CC BY-SA 3.0