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.
The pocket flattened out, and became two pieces of cloth, one solid (the one at the back) and the other shaped almost like a 'U'. The pocket was also attached to its own belt, usually cloth at this time, and was often elaborately embroidered and decorated. You can still see some of these beautiful works of pocket artistry in museums that are dedicated to original period costumes.
However, if history had been left to the rich and carefree who had time to make and elaborate on the undergarment pocket, then our pocket history might have ended there. In many ways, that would have been a prettier solution. Imagine, pocket factories, we'd have them made out of all sorts of materials; after all, they were often right up next to the skin. Angora pockets, velour pockets, pockets made of polar fleece with silken tassels on the bottoms, etc...
The Modern Pocket
Looking to the modern pocket, we must go back to the trousers again. We are now in the late 1700s. Let's say it's 1784 before some poor soul gets sick and tired of having to remember to tie his pocket on every day before he gets dressed. Most likely, you know a person like this. This is a person who has problems remembering to put his trousers on before his shoes, let alone remembering to tie his pocket on before his trousers.
Yet, absent minded as he is, he is no dunce. Therefore, in a fit of pique, he asks his wife to sew the pocket right to his trousers so he will never forget it again. And suddenly, there you have it. The pocket. The real, true, ultimate pocket. The friendly pocket you and I know and love that has been our most intimate friend since childhood... warming cold hands or holding fluff, bits of string and useless notes from friends long past and best forgotten.
The pocket has gone through many changes since that fateful day. People have placed pockets in other places than the waist: on the knee, on the thigh, and at the chest (the infamous 'breast pocket'). People have even returned to the practice of inside pockets, again requiring people to pull down their trousers and moon the supermarket in order to get at their cash (though, thankfully, that is very rare).
Types and Uses of Modern Pockets
The modern pocket is a tool with various uses and styles, and it can be found in almost every article of men's and women's casual attire in a variety of forms. Here are just a few examples:
Watch-pocket - Essential for keeping a gentleman's pocket watch. Often found on the man's vest or even on his trousers. The watch had a chain or a fob, to prevent it from being lost, and this pocket sometimes could be called the 'fob pocket'.
Breast pocket - Located on the outer left-hand side of a gentleman's jacket, it must contain nothing more than a pocket-handkerchief and is for display only.
Inner breast pocket - Found on the inside of the jacket. It's normal to have two of them, for carrying a wallet or pen, or legal papers such as a passport.
Ticket pocket - This is a small pocket inside the right-hand waist pocket on a jacket and was used in previous times for carrying small cardboard rail tickets. These days, it might be used to store your business cards or other light items (such as a lucky coin).
Coin pocket - This is a small pocket inside the right-hand hip pocket on a pair of jeans. It's a rather tight fit, but its design is quite effective at keeping your loose coins from rattling around.
Cargo pockets - These pockets appear commonly on trendy jeans and cargo pants as a large pocket on the thigh, usually with snap-flaps or Velcro flaps, and accordion folds in the sides for increased capacity. It's believed these first appeared on battledress uniforms.
There are various other pockets of note, such as hip pockets, thigh pockets, etc. Other pockets with specific uses include a mobile pocket on a woman's purse for carrying a mobile phone (which are often unsightly-looking afterthoughts of pockets, carelessly sewn on the outside of the purse) and the unusual 'mitten pocket' found on some woolen scarves, for storage of the matching mittens.
The Figurative Pocket
The word 'pocket' also can refer to many things in life besides what is mentioned above. As a part of speech, it has found its way into almost every aspect of modern life, referring to objects that are smaller than normal (pocket-sized) such as the 'pocket mouse' and 'pocket gopher' - two distinct species of rodents with large external cheek pouches (these are common in the Americas).
In the financial area, there are many terms that make good use of 'pocket', such as 'pocket money' and 'to touch the pocket'. Also, 'pocket piece' is a piece of money kept in the pocket and not spent.
In politics, a 'pocket borough' is a borough with very few voters. Before the parliamentary reform in 1832, it was a small borough controlled by a single family or person. As well, a 'pocket sheriff' is a sheriff appointed by the sole authority of the crown, without a nomination by the judges in the exchequer.
In other areas of life: a 'pocket pistol' is not a firearm, but a flask of whisky carried just in case no drink is available on a journey. In addition, the popular video game series Pokemon is derived from the words 'pocket monster'. In mining, a 'pocket' is a rich deposit of ore found in a cavity in rock. In sailing, a 'pocket' is a strip of cloth sewn onto a sail through which a spar or batten can be inserted. In billiards, it is the pouch into which the balls are driven.
And so, for all of you who thought you knew all about the pocket... think again. It is an elusive creature, hiding deep in the folds of the clothing of time, and it is clear that it still has a long way to go to make itself useful and accessible to all. Now you know.
You may also be interested to read about the history of the handbag.