1870, "a rustling," from French (19c.), possibly imitative of the rustling of a dress. Meaning "fussy details" is from 1876.
Online Etymology Dictionary, © 2010 Douglas Harper
Examples from the Web for frou-frou
Frou-frou is a creature that can love, can suffer, can repent, can die.
But Frou-frou is in no sense the true Femme Galante of her day.
Frou-frou, who stands for her, is not in the least the true type.
But before we left him he insisted that we should sit through his favourite "Frou-Frou."Poor Folk in Spain
We can almost hear the frou-frou of their garments in his pictures.Watteau
C. Lewis Hind