-on, plural -a, is just the ordinary second declension neuter nominative/accusative ending. It's about as common as a linguistic phenomenon can be. Etymologica

-on, plural -a, is just the ordinary second declension neuter nominative/accusative ending. It's about as common as a linguistic phenomenon can be. Etymologically, you'd expect it to apply to the physics particles named for qualities, like photon, but I don't think that's ever done.