The origin of ihai is said to have come from the syncretization of the folkways of yorishiro (an idea in which a divine spirit resides in an object) and the sotoba (a tall, tower-shaped wooden tablet set up behind a grave for the repose of the dead) in Buddhism.
またその起源は、霊の依代（よりしろ）という古来の習俗と仏教の卒塔婆が習合した物ともされる。