how to learn defense skill in Caveman 3.0

the game: Caveman v3.0. a FPSRPG / person sim hybrid. stone age setting. emphasis on realism.

i recently added a "defense" skill to the game.

like the game Traveller, in Caveman, your hit points never go up. you may get better at combat, but you can't just magically take more physical damage for some reason. a cracked skull is still a cracked skull.

but you should become harder to kill as you get better at combat. so i added the defense skill that goes up every time you're attacked, and represents being more experienced at being attacked and avoiding being hit for damage. the effect of the skill is to reduce the chance of you're being hit.

the game uses FPS shooter type combat to determine if a hit could occur, and then uses RPG stats and dice rolls type combat to resolve the potential hit.

the game already has a number of offensive weapon specific skills, such as slash and stab attack and a separate skill for almost every type of missile weapon.

so the questions are:

should it be "combat" instead of "defense" skill?. the name is not set in stone.

how should the player be able to learn the defense skill? all i've come up with so far is fencing with sticks, which requires a second willing caveman nearby.