A pocket is a bag- or envelope-like receptacle either fastened to or inserted in an article of clothing to hold small items. Pockets may also be attached to luggage, backpacks, and similar items. In older usage, a pocket was a separate small bag or pouch.
Ancient people used leather or cloth pouches to hold valuables.Ötzi (also called the "Iceman"), who lived around 3,300 BCE, had a belt with a pouch sewn to it that contained a cache of useful items: a scraper, drill, flint flake, bone awl, and a dried fungus.
In European clothing, fitchets, resembling modern day pockets, appeared in the 13th century. Vertical slits were cut in the super tunic, which did not have any side openings, to allow access to purse or keys slung from the girdle of the tunic.
In slightly later European clothing, pockets began by being hung like purses from a belt, which could be concealed beneath a coat or jerkin to discourage pickpocketing and reached through a slit in the outer garment.
The word appears in Middle English as pocket, and is taken from a Norman diminutive of Old French poke, pouque, modern poche, cf. pouch. The form "poke" is now only used dialectically, or in such proverbial sayings as "a pig in a poke".
Historically, the term "pocket" referred to a pouch worn around the waist by women in the 17th to 19th centuries, mentioned in the rhyme Lucy Locket.
A watch pocket or fob pocket is a small pocket designed to hold a pocket watch, sometimes found in men's trousers and waistcoats and in traditional blue jeans. However, due to the decline in popularity of pocket watches, these pockets are rarely used for their original intended purpose.
...
Wikipedia