When a little recovered, he fribbled with his waistcoat buttons, as if he had been telling his beads.
-- Samuel Richardson, Clarrisa, 1748
He fribbled away his time collecting bric-a-brac and drinking tea with old ladies; yet wrote the best letter; in the language in the midst of the chatter; knew everyone; went everywhere; and, as he said, "lived post."
-- Virginia Woolf, The Death of the Moth and Other Essays, 1942
Fribble is most likely a variant of the more common word frivol meaning "to behave frivolously."