In today's field of gaming, the humble mana bar has become nearly as widespread as the health bar. Everywhere from MMOs to flash games, to traditional turn-based RPGs, Mana exists as a finite consumable resource (often a blue bar) used to cast spells and/or abilities.
And yet, the biblical definition of mana has little to do with the term as it exists in modern-day vernacular.
Tolkien or Dungeons and Dragons are the usual culprits for widespread fantasy terms (dwarves come to mind), but neither Tolkien nor any version of Dungeons and Dragons make mention of mana (Tolkien downplayed magic in general, and D&D has traditionally used the concept of "spells per day"), so the origin of the term remains unknown to me.
So where or when did "Mana" first become used in this modern, videogame-inclined sense?