Ceruleum is supposedly energy drained from crystals. I always thought of magitek as meaning the imitation of magic via technology, since members of the garlean race are genetically unable to control aether (use magic) naturally.

Aether could be described as the worlds energy, life, nature and the elements which can be manipulated by many races to conjure up spells and power magic based technology, perhaps even assisting in forging or building.