I'm pretty sure that it's not an enchantment but a useable item that adds 100 HP to either the head or the legs. There aren't any enchantments that work on the head/legs that I know of.
aside form the Libram's(books that when combined with items make a item that will buff helm and leg) the Agent Dawn has a sholder enchant item, and the good old ZG trolls have a slew of buffs to hats and pants.