The Collaborative International Dictionary of English v.0.48:

Sol-fa \Sol`-fa"\, v. i. [imp. & p. p. Sol-faed;p. pr. & vb.
   n. Sol-faing.] [It. solfa the gamut, from the syllables fa,
   sol.]
   To sing the notes of the gamut, ascending or descending; as,
   do or ut, re, mi, fa, sol, la, si, do, or the same in reverse
   order.
   [1913 Webster]

         Yet can I neither solfe ne sing.         --Piers
                                                  Plowman.
   [1913 Webster]