mid-14c., pokete, "small bag or pouch, small sack," from Anglo-French pokete (13c.), diminutive of Old North French poque "bag" (Old French pouche), from a Germanic source akin to Frankish *pokka "bag," from Proto-Germanic *puk- (see poke (n.1)).
The narrower meaning "small bag worn on the person, especially one sewn into a garment" is from early 15c. The sense of "one of the small bags or nets at the corners and sides of some billiards tables" is from 1754. The mining sense of "cavity in the ground filled with ore" is attested from 1850; the military sense of "area held by troops almost surrounded by the enemy" is from 1918; the general sense of "small area different than its surroundings" (1926) apparently was extended from the military use.
Figuratively, "one's money" (conceived as being kept in a pocket), from 1717; hence to be out of pocket "expend or lose money" (1690s); Pope Pokett (late 15c.) was figurative of the greedy and corrupt Church.
1580s, "to place in a pocket or one's pocket" (often with implications of dishonesty, "to appropriate to one's self or for one's own use"), from pocket (n.). From the earliest use often figurative. Meaning "to form pockets" is from c. 1600. Related: Pocketed; pocketing.
1610s, "of or pertaining to or meant for a pocket," from pocket (n.). Pocket-money "money for occasional or trivial purposes" is attested from 1630s; pocket-handkerchief is from 1640s. Often merely implying a small-sized version of something (for example of of warships, from 1930; also compare Pocket Venus "beautiful, small woman," attested from 1808). Pocket veto attested from 1842, American English.
The "pocket veto" can operate only in the case of bills sent to the President within ten days of Congressional adjournment. If he retain such a bill (figuratively, in his pocket) neither giving it his sanction by signing it, nor withholding his sanction in returning it to Congress, the bill is defeated. The President is not bound to give reasons for defeating a bill by a pocket veto which he has not had at least ten days to consider. In a regular veto he is bound to give such reasons. [James Albert Woodburn, "The American Republic and its Government," Putnam's, 1903]
In English history a pocket borough (by 1798) was one whose parliamentary representation was under the control of one person or family.
BRAMBER, Sussex. This is one of the burgage-tenure or nomination boroughs. The place altogether consists only of twenty-two miserable thatched cottages, and is composed of two intersections of a street, the upper and middle parts of which constitute another pocket borough, called Steyning, which we shall notice in the second class, as belonging to the Duke of Norfolk. ["A Key to the House of Commons," London, 1820]