The Collaborative International Dictionary of English v.0.48:

Fa \Fa\ (f[aum]), n. [It.] (Mus.)
      (a) A syllable applied to the fourth tone of the diatonic
          scale in solmization.
      (b) The tone F.
          [1913 Webster]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

FA
       FernmeldeAmt (DTAG)