Few things are exact about the nature the Thu'um. It resembles the more fundamental concept of CHIM in that both allow mortals to alter reality by knowing certain words. That the Thu'um requires the dragon language possibly points to an origin in Akatosh, though the power might also be connected with Kyne. In any case, how it dose or dose not work is divinely dictated for a purpose, as is every natural law in Mundus.

UESP page for Thu'um

UESP page for CHIM