In ancient Rome, Os impurum, "filthy mouth" or "impure mouth", was a term of abuse especially for those who provided oral sex. [Wikipedia "Sexuality in ancient Rome"]
My couch sex was interrupted by a couple Jehovah's Witnesses. Not mormon missionaries, but still. The fuckers rang the doorbell *and* knocked when I ignored (continued fucking my boyfriend) them. Answered it and the poor guy is going to have impure though
