Jack

Jack pet name of the given name John. The term was originally (in late Middle English) used to denote an ordinary man, and in the mid 16th century, a youth, hence the knave in cards, and the use of the word to denote a male animal. The word is also used for a number of devices saving human labour, as if one had a helper. The general sense of ‘labourer’ arose in the early 18th century, and since the mid 16th century, the notion of ‘smallness’ has arisen.
every Jack has his Jill all lovers have found a mate; proverbial saying, early 17th century.
Jack and Jill a nursery rhyme, in which Jack and Jill, who go up a hill for water, both fall down, with Jack breaking his crown and Jill tumbling after; it has been suggested that the origin is political, with Jack and Jill representing Henry VII's ministers Empson and Dudley, who were executed soon after Henry VIII's accession. An alternative explanation is that the rhyme is of Scandinavian origin, in the story of two children (Hjuki and Bil) who were stolen by the moon while drawing water. In North American usage, a Jack and Jill party is a party held for a couple soon to be married, to which both men and women are invited.
Jack and the Beanstalk a fairy story, recorded from the mid 18th century, about a poor boy who sells his mother's cow for a handful of beans; she throws them angrily away, but the ones that have fallen into the garden root and grow into an enormous plant. Jack climbs the beanstalk, and discovers a ferocious giant; with magic help, he first steals from the giant and then by a trick contrives his death. A beanstalk is proverbially fast-growing, but in this story it may also represent the Norse world-ash Yggdrasil.
Jack Frost a personification of frost; recorded from the early 19th century.
Jack Horner a nursery-rhyme character, ‘Little Jack Horner’, said to have ‘pulled out a plum’ from a ‘Christmas pie’; it has been suggested that this refers to a real Jack Horner who cheated his way into property at the dissolution of the monasteries.
jack-in-office a self-important minor official; the term is recorded from the early 18th century.
jack-in-the-box a toy consisting of a box containing a figure on a spring which pops up when the lid is opened; the term is recorded from the early 18th century.
Jack-in-the-green a man or boy enclosed in a wooden or wicker pyramidal framework covered with leaves, in traditional May Day celebrations.
Jack is as good as his master proverbial saying, early 18th century; Jack is used variously as a familiar name for a sailor, a member of the common people, a serving man, and one who does odd jobs.
Jack of all trades and master of none a person who has simple skills in a number of areas is not fully competent in any of them; Jack here is used in the sense of an unskilled worker, as contrasted with a master of a trade who had completed an apprenticeship. The saying is recorded from the mid 18th century.
jack-o'lantern originally a man with a lantern, a night watchman; from this, an ignis fatuus or will-o-the-wisp. The term in these senses is recorded from the 17th century. From the mid 19th century, jack-o'-lantern has also been used (originally in the US) for a lantern made from a hollowed-out pumpkin or turnip in which holes are cut to represent facial features, typically made at Halloween.
Jack Russell a terrier of a small working breed with short legs, named after the Revd John (Jack) Russell (1795–1883), an English clergyman famed in fox-hunting circles as a breeder of such terriers.
Jack Sprat, in the 16th and 17th centuries, a name for a very small man, a dwarf; in the nursery rhyme, recorded from the late 17th century, Jack Sprat is the husband who ‘could eat no fat’, while his wife ‘could eat no lean’.
Jack tar an informal name for a sailor, recorded from the late 18th century.
Jack the Giant-killer a nursery tale of Northern origin, known in England from very early times. Jack was said to be the son of a Cornish farmer, living in the days of King Arthur, who by his ingenuity acquired a coat that made him invisible, shoes which gave him great speed in running, and a magic sword. With the help of these, he destroyed all the giants in the land.
Jack the Ripper was an unidentified 19th-century English murderer. In 1888 at least six prostitutes were brutally killed in the East End of London, the bodies being mutilated in a way that indicated a knowledge of anatomy. The authorities received taunting notes from a person calling himself Jack the Ripper and claiming to be the murderer, but the cases remain unsolved despite a wide variety of names being suggested.

See also a good Jack makes a good Jill, the House that Jack built at house, Jack Ketch, all work and no play makes Jack a dull boy.