Having a date for "The Twelfth" of 1861-62, And Martin giving us a date of 1840 for "Clare's Dragoons" (Thomas Osbourne Davis died in 1845), clarifies the fact that "The Twelfths" is derivative of "Clare's Dragoons".
It would seem that Archibald Scott intended to have his name associated with "the air: Viva la". This, though, was presumably the same tune already in use for "Clare's Dragoons".