Tennis Buttock

• dumper sometimes denotes the buttocks, especially when talking about a large butt.
• fanny - a socially acceptable term in print, in the United States at least, for many years before some of the bolder terms came along; and a subject of jokes, since "Fannie" can be a woman's name, diminutive of "Frances"; however, in British English fanny refers to the female genitals or vulva and is considered vulgar. The figure of a bare-bottomed lass named Fanny is ubiquitous in Provence (the southeast of France) wherever pétanque is played: traditionally when a player loses 13 to 0 it is said that “il est fanny” (he's fanny), and he has to kiss the bottom of a girl called Fanny; as there is rarely an obliging Fanny, there is always a substitute picture, woodcarving or pottery so that Fanny’s bottom is always available.
• fourth point of contact: in military slang, because of the sequence of textbook parachute jump landing
• fundament (literally "foundation", not common in this general sense in English, but for the butt since 1297)