The word originated from Old English meaning ears. It now has a slang meaning of “the butt”. As a derogatory term it means “ass” and an insult. Nowadays when you call someone an arse, you mean to call them an asshole.
Twat first originated in British English as an offensive word. Their are not many non offensive meaning for the word, but many different offensive meanings. In it’s offensive form, it can mean childish, an insult, or drunk. Nowadays when you call someone a twat, you mean to call them a fool.
A Douche is a medical device in the dictionary. The word was put in to slang in the 1960′s and is not very popular today, but still in use. In slang, it means a person with negative qualities. Nowadays when you call someone a douche, you mean to call them arrogant.
Faggot came from the word Fag. Fag can mean servant, weak and unmanly. Faggot is a slang pejorative term for a homosexual. Nowadays when you call someone a faggot, you mean to call them a queer.