I think the ones mentioning Gambler are possibly on the right track, considering that was how Corsair worked in FFXI with "dice rolls" and essentially you gambled to either roll again for a higher number with the risk of going bust and getting no benefit and you lose the ability to have 2 buffs on the party or just staying put at a lower number for a lesser effective buff.

Although what I assumed was his t-shirt had a Pistol on it and as such musketeer will use a pistol instead of perhaps a larger rifle or mage type gun weapon.