Source : Webster's Revised Unabridged Dictionary (1913)

Spavin \Spav"in\, n. [OE. spaveyne, OF. esparvain, F.
   ['e]parvin; akin to OF. espervier a sparrow hawk, F.
   ['e]pervier, fr. OHG. sparw[=a]ri (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.

   {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.

Bog \Bog\, n. [Ir. & Gael. bog soft, tender, moist: cf. Ir.
   bogach bog, moor, marsh, Gael. bogan quagmire.]
   1. A quagmire filled with decayed moss and other vegetable
      matter; wet spongy ground where a heavy body is apt to
      sink; a marsh; a morass.

            Appalled with thoughts of bog, or caverned pit, Of
            treacherous earth, subsiding where they tread. --R.
                                                  Jago.

   2. A little elevated spot or clump of earth, roots, and
      grass, in a marsh or swamp. [Local, U. S.]

   {Bog bean}. See {Buck bean}.

   {Bog bumper} (bump, to make a loud noise), {Bog blitter},
   {Bog bluiter}, {Bog jumper}, the bittern. [Prov.]

   {Bog butter}, a hydrocarbon of butterlike consistence found
      in the peat bogs of Ireland.

   {Bog earth} (Min.), a soil composed for the most part of
      silex and partially decomposed vegetable fiber. --P. Cyc.

   {Bog moss}. (Bot.) Same as {Sphagnum}.

   {Bog myrtle} (Bot.), the sweet gale.

   {Bog ore}. (Min.)
      (a) An ore of iron found in boggy or swampy land; a
          variety of brown iron ore, or limonite.
      (b) Bog manganese, the hydrated peroxide of manganese.

   {Bog rush} (Bot.), any rush growing in bogs; saw grass.

   {Bog spavin}. See under {Spavin}.

Source : WordNet®

bog spavin
     n : spavin caused by collection of fluids