Mother fucker

Etymology:
One of the top three no-nos (along with cunt and fuck) and use at any time of day on live television can get you shitting well fired. The etymology is North American, mid 20th Century and it’s quite obvious why it’s offensive. It maintains its meaning in most regions apart from Texas, St Helens, Northampton and the Orkneys, where it is actually an endearment or grim statement of fact.

Essential use in cinema: Casino
Joe Pesci gets all the best swearing lines in Martin Scorcese films but nothing quite beats his rejoinder to a cowboy hat wearing gambler who has his feet on some furniture: “You shit-kicking, stinky, horse-manure-smellin' motherfucker you. You fuck me up over there, I'll stick you in a hole in the fuckin' desert.”