spavin
noun
spav·in ˈspa-vən 
: swelling
especially : a bony enlargement of the hock of a horse associated with strain
Word History
Etymology
Middle English spavayne, from Middle French espavin, alteration of Old French esparvains, probably of Germanic origin; akin to Old High German sparo sparrow (likened to a lump)
First Known Use
15th century, in the meaning defined above
Medical Definition
spavin
noun
spav·in ˈspav-ən
: osteorarthritis of the hock of a horse