In your younger days, you waded into battle as a mercenary, a warrior defending a nomadic people, or a member of a militia or army. You might have wanted to break out from the regimented structure of these forces, or you could have always been as independent a warrior as you are now.
Choose two ability boosts. One must be to Strength or Constitution, and one is a free ability boost.
Source: Pathfinder Core Rulebook (Second Edition)