fornicating unlawful cardinal knowledge: its use came around in the early years of the French revolution. It was written on the walls of the Bastille, before the French bourgeoisie tore it down.
In today's culture, it can mean a variety of things, such as replacing other words when one is inarticulate, or often referring to its verb form, to have sex with someone. It can also be used as an adjective with negative or positive connotation.
A word that can be used in every sentence in any part of the sentence. It can be used to express anger, love, sadness, disappointment, or really any emotion in the world.