The Collaborative International Dictionary of English v.0.48:

Frivolity \Fri*vol"i*ty\, n.; pl. Frivolities. [Cg. F.
   frivolit['e]. See Frivolous.]
   The condition or quality of being frivolous; also, acts or
   habits of trifling; unbecoming levity of disposition.
   [1913 Webster]