Tennis Buttock

• prat (British English, origin unknown; as in pratfall, a vaudeville term; also a term of abuse for a person)
• seat (of the trousers; or metaphorically) another long-standing socially acceptable term, referring to the use for sitting - but compare the sarcastic use of seat of wisdom and similar expressions, such as 'seat of learning', referring to use as target for an 'educational' spanking.
• sit-upon; has various independent counterparts in other languages, e.g. Dutch zitvlak ('sitting plain'), German Gesäß Italian sedere
• six; in military terminology, particularly in the U.S. Navy, it refers to the term "six o'clock", i. e. a point directly behind the referenced person.