According to Hoyle

A phrase used to emphasize the proper rules of a game, as in "We played without wild cards or other non-standard variations — it was all strictly according to Hoyle."

Named for Edmond Hoyle who authored numerous books about card games in the 18th century, with his name oft-used afterwards in titles of later books of card game rules. Even though poker was not invented until well after Hoyle's death in 1769 (in the early 19th century), he was nonetheless inducted into the Poker Hall of Fame as a recognition of his status as a card game authority.