Frabjous and versipel are both invented words. Frabjous you most likely recognize from Lewis Carroll’s “Jabberwocky” (the Urban Dictionary defines it, delightfully, as “like fabulous, but with a lemon twist”).
Versipel is a back-formation Nabokov uses in Pale Fire, from versipellous (“changeable; protean; having a form, nature or appearance that changes often”):
And that odd muse of mine,
My versipel, is with me everywhere,
In carrel and in car, and in my chair.
This is where I log my journeys with my own frabjous, changeable muse.