The Collaborative International Dictionary of English v.0.48:

Trifoly \Tri"fo*ly\, n. [L. trifolium. See Trifoliate,
   Trefoil.] (Bot.)
   Sweet trefoil. [Obs.]
   [1913 Webster]

         She was crowned with a chaplet of trifoly. --B. Jonson.
   [1913 Webster]