Although, there are various arguments concerning interpretation of 'shikigami,' with one of them being that it is like the esoteric Buddhism Goho-doji or with another being that it is to make use of spirits, but the most compelling theory seems to be that it originated from 'Rikujinshikiban' used in Onmyodo.
「式神」の解釈は密教の護法童子に似たものであるとか、精霊を使役するものであるとか諸説存在するが、最も有力なのは陰陽道で用いられる「六壬式盤（りくじんしきばん）」に由来するとの説であろう。