From the experts:
Finnian is a fair jig of a name, energetic and easy on the ear. Finnian (and brother Finian) is also familiar in its alternate spelling through the classic 1968 Broadway musical Finian's Rainbow, later made into a film starring Fred Astaire as Finian McLonergan.
There is also a St. Finnian who was a famous teacher and scholar.
We think Finnian/Finian could really catch on in the wake of cousins Finn and Finlay/Finley.