Aniol is a Catalan name, not Spanish (the Spanish form is Aniano and the Basque form is Anen).
Aniol is the evolution: a) from the Latin Andeoli/Andeolus (meaning unknown) (according to Josep M. Albaigès and Idescat). The Latin group -ND- evolves to -NN- (gemination) and, finally, reduces to -N- (reduction) in Catalan. b) from the Latin cognomenAn(n)ianus, derivated from Annius, Latin gens related with the goddess Anna Perenna (according to Roberto Faure and Consuelo García Gallarín).
Yes, this is a saint name; in fact, there are several saints named Aniol. And in Catalonia is quite popular as first name (#126 in 2002), specially at Ripollès and la Selva (Catalan regions).
Regarding Aniol in place names, in Catalonia there are some places called "Sant Aniol". Sant Aniol de Finestres and Sant Aniol d'Aguja are the most popular.
NOTE: sant is the Catalan word for the Spanish san or santo, then a place called "Sant somewhere" is a Catalan place name (in Spanish, this will be "San somewhere").