Philippa is a prime example of a boy's name adapted for girls that was common as crumpets in Cornwall, but rarely heard stateside, never having appeared in the Top 1000. That was before the advent of royal sister-in-law Philippa Middleton, who goes by the lively nickname Pippa.
Philippa has been fashionable in England since the fourteenth century when King Edward married Philippa of Hainault. There have been several early Saint Philippas, and it was the name of the wife of Geoffrey Chaucer.
Novelist Philippa Gregory authored the bestselling historical novel The Other Boelyn Girl.