Saddlebags

[Sarah]

Bags, usually of leather, united by straps or a band, formerlymuch used by horseback riders to carry small articles, one baghanging on each side.

[Sarah]

Sheesh! I have seen this phrase misused a few times now (even in Roger Mellie's Profanisaurus!). Let me clear things up:
Saddlebags is a word to describe the bulging areas of fat on the upper outer thighs of ladies, in a way that resembles saddle bags being carries on a horse.

[Vania]

a small bag that you fix to the back of your bicycle saddle, or one of a pair of bags that you put over the back of a horse or over the back wheel of a bicycle or motorcycle