Strength, made from Amn + Tir, in that order. This works in two-socket melee weapons. Possible in v1.08 and above.
Not huge damage added, just 35%, but nice bonuses to other things makes this a useful all around weapon for the low-mid level character. The Crushing Blow will certainly make it more useful later in the game though. The Clvl 37 is from the Greater Claws used here, that's their requirement, not the RuneWord's. The bonus to Assassin skills are from the claw used in the recipe, they aren't part of the RuneWord bonus either.
Weapons Runewords