Willoughby is an energetic last-name-first route to the popular short form Will, livelier than any of the two-syllable options. It could be picked up by parents attracted to the Willow sound for girls.
Willoughby Patterne is the protagonist of the George Meredith novel, The Egotist. Willoughby Sharp was a contemporary artist, curator, critic and founder of the seminal art magazine, Avalanche. There is a classic 1962 British children's novel titled The Wolves of Willoughby Chase by Joan Aiken that was made into a film in 1989.