The Collaborative International Dictionary of English v.0.48:

Lather \Lath"er\, v. t. [imp. & p. p. Lathered
   (l[a^][th]"[~e]rd); p. pr. & vb. n. Lathering.] [AS.
   l[=e][eth]rian to lather, anoint. See Lather, n. ]
   To spread over with lather; as, to lather the face.
   [1913 Webster]