Coming from Kakegoto (gambling) and Shobugoto (game), Tomobiki is considered to mean 'draw with a friend in Shobugoto' derived from mixing with Onmyodo (way of Yin and Yang; occult divination system based on the Taoist theory of the five elements).
賭け事、勝負事から入って来ており、友引とは「勝負事で友人と引き分ける」という意とされ、陰陽道との混淆に由来する。