Could be opposed Agility or Strength, whichever the player prefers? It represents either a powerful grip or leveragimg your body to its maximum.

Bertelis has ~50% agility, guy is pretty quick and graceful, yet a goblin has a good chance of resisting his attempts at a grapple and wasting his turn.

The Disarm talent (which Im taking for Regine soon) is an opposed agility test after hitting with an attack, becsuse it's a competition between two sides.