Perhaps it dates from the Riverdance phenomenon? Didn't many of the girl dancers in the various stage shows spawned by the above-mentioned show have bouncy curls? However I don't think they were the extreme curls of current times, and they weren't worn by little girls but by adult dancers.

And as for the frocks....the description above of vomiting the Book of Kells is great.

Cheers
JennieG