Fornicating Under consent of the King, or Fuck, dates back to the middle ages when people had to ask permission from the king to have sex.

this is the expanded abbreviation of the word or slang term which is FUCK.
a long time in England, one would need to get 'consent' from the king, if a couple would ever want to have sex or have a child (this is not including nobility or royalty)

in Europe in the olden-days...

if a man wanted to sleep with a woman and she says "no" he can go to the king and if he says it is okay, the woman HAD to sleep with the man.

Fornication Under Consent of the King=FUCK

an elaborate and/or fancy way to tell someone to fuck a cactus

The letters at the beggining of each word basically spell FUCK

a term used to describe moving in with your lover with the expressed agreement that no sexual activities will ensue before marriage. Similar to "taxation without representation" but with a sexual aspect.

When a black midget woman and a white midget man have consensual sex. The white midget man pulls out and cums in the black midget womans mouth. Then the white midget man slaps the black midget woman on the back of the head causing the black midget woman to spit the cum everywhere.