Spavin (?), n. [OE. spaveyne, OF. esparvain, F. éparvin; akin to OF. espervier a sparrow hawk, F. épervier, fr. OHG. sparwāri (G. sperber), fr. OHG. sparo sparrow, because this disease makes the horse raise the infirm leg in the manner of a sparrow hawk or sparrow. See Sparrow.] (Far.) A disease of horses characterized by a bony swelling developed on the hock as the result of inflammation of the bones; also, the swelling itself. The resulting lameness is due to the inflammation, and not the bony tumor as popularly supposed. Harbaugh.
[1913 Webster]

Bog spavin, a soft swelling produced by distention of the capsular ligament of the hock; -- called also blood spavin. -- Bone spavin, spavin attended with exostosis; ordinary spavin.
[1913 Webster]