In ancient England a person could not have sex unless you had consent of the King (unless you were in the Royal Family). When anyone wanted to have a baby, they got consent of the King, the King gave them a placard that they hung on their door while they were having sex. The placard had F.U.C.K. (Fornication Under Consent of the King) on it.
LOL WTH imma say “fornication under consent of king YOU” now :3