The Collaborative International Dictionary of English v.0.48:

Falsetto \Fal*set"to\, n.; pl. Falsettos. [It. falsetto, dim.
   fr. L. falsus. See False.]
   A false or artificial voice; that voice in a man which lies
   above his natural voice; the male counter tenor or alto
   voice. See Head voice, under Voice.
   [1913 Webster]