Why is the word rack slang for breasts?

Answer 1

It is wise not to ask too many questions about idioms and slang. Many times there are no reasons for them. This is not opaque to begin with. A rack is a shelf that holds items of various size. A spice rack is an example. Since a woman's breasts are held up like bottles of spice on a rack, they have been referred to as a rack.

While it's true that there are slang terms and idioms that have baffling or uncertain origin, it is interesting and informative to know that origin, in the cases where it can be found, for the simple reason that it quite often gives a fascinating perspective on history that you won't necessarily find in a textbook. And quite a few of our slang/idiomatic phrases do have historical rationale behind them, some going back earlier than the Roman Empire. Two interesting sources are the Online Etymology Dictionary or any of the available lists of nautical sayings (e.g, 'let the cat out of the bag').

For example, the first resource above has an alternative attribution for the use of the term 'rack' as slang for a woman's breasts. Evidently, the term was originally adopted by hunters as slang for the highly branched antlers of some ungulates such as deer and elk. Of course, large antlers are a readily observable gender distinction for these animals. By extension, since breasts are a readily observable gender distinction for women (hence it might said that breasts declare a woman's gender as antlers declare an elk's gender), 'rack' evolved to apply to breasts over the course of the following decades. It's an interesting case of a slang term that appeared for one particular use and then later loosened and broadened its use. This is probably unsurprising since hunting is a male social group activity in western cultures (and others), and male social groups are precisely where pretty much all slang terms regarding women arise.

Answer 2

Because Tom Leykis says so.

Answer 3

Because Tom Leykis said so.