Yes, you read that right: the pocket. From the BBC (yes, you read that right too):
To begin with, the definition of the word ‘pocket’ states that it is ‘a small baglike attachment’. The reason for this particular definition is that the pocket was not originally sewn into garments as it is today. In fact, the first pockets were actually small pouches that hung from the belt where one could carry valuables and coins. The word itself comes from the Anglo-Norman word pokete and traces its roots to the Germanic root word ‘bag’, which is like the Old English word pocca. Therefore, the definition makes sense. ‘Purse’ and ‘pocket’, incidentally, have the same root word, only one is plural and the other singular.
In addition and worthy of note is the Scottish sporran, which is that nifty purse worn at the front of the kilt in traditional wear. The word sporran itself comes from the old Irish word sparán, which traces its roots back to the Latin word bursa, or ‘purse’.
The First Interior Pockets
Since the pocket was on the outside of one’s clothing, it was unfortunately subject to thieves or, more appropriately, cut-purses. More cautious people realised that if they kept their purses inside their trousers1, it would deter the pickpockets by making the theft more difficult.
But, there came a realisation: Although keeping one’s pouch inside of one’s clothes made it more difficult for thieves to get at the pouch, it also made it more difficult for the owner of the purse to get at the contents! And as the point of the purse in the first place was to make it easy to carry one’s money, making it impossible to get at without embarrassment was not the greatest of solutions. Imagine, there you are, in the common market, and you want to buy yourself an apple. In order to buy it you must drop your trousers and expose your buttocks to the entire marketplace! (Note: In that day and age, not only did people not have interior pockets, but they also did not wear undergarments!)
The next step in the evolution of the pocket was what most people see them as today: a simple slit in the clothing. A slit cut into the side of your trousers (or by that time your skirt as well, as women have never been known for dropping their skirts in the marketplace… much) would enable you to reach into your purse with ease, while others would find it difficult to reach in without your knowledge and acquiescence. This development of the clothes slit caused a revolution in the shape and the angle of the opening in the purse, and it was around that time that they began to be called pockets. . . .
For the rest of the story, click here (though you can probably see where this is going).