Oracle Text

Whenever a noncreature source you control deals damage, you gain that much life.

Card Rulings

7/15/2006 A noncreature source is a source that doesn’t have the type creature. If a creature card that’s not on the battlefield deals damage (for example, a cycled Gempalm Incinerator), Tamanoa’s ability won’t trigger.
7/15/2006 Tamanoa’s ability triggers no matter who the recipient of the damage is: another player, a creature, or even you. If a noncreature source you control deals damage to you that drops your life total to 0 or less, you’ll lose the game before Tamanoa’s ability can resolve.