Source : Webster's Revised Unabridged Dictionary (1913)

Wittol \Wit"tol\, n. [Said to be for white tail, and so called
   in allusion to its white tail; but cf. witwal.]
   1. (Zo["o]l.) The wheatear. [Prov. Eng.]

   2. A man who knows his wife's infidelity and submits to it; a
      tame cuckold; -- so called because the cuckoo lays its
      eggs in the wittol's nest. [Obs.] --Shak.