According to one theory, the idea was that Tokoyo referred to tokoyo (written as 床世 in Chinese characters; 床 also means sexual activities), and the sexual activity was a sacred one conducted in the sacred area (or inviting people to the sacred area).
一説には常世は床世（床は性行為の意味もある）であり、性行為は神域で行われる（若しくは神域へ誘う）神聖なものとする考え方がある。