JACK, a word with a great variety of meanings and appli cations. In the History of the Monastery of St. Augustine at Canterbury, 1414, Jack is given as a form of John—"pro Johanne Jankin sive Jacke" (see E. W. B. Nicholson, The Pedigree of Jack and other Allied Names, 1892). was early used as a general term for any man of the common people. The New Eng lish Dictionary quotes from the Coventry Mysteries, 1450: "And I wole kepe the feet this tyde Thow ther come both Iakke and Gylle." Jack or Jack Tar for a sailor seems to date from the 17th century, and such uses as steeple-jack, "jack of all trades," etc. may be noted. It is a further extension of this that gives the name to the knave in a pack of cards, and also to various animals, as jack-snipe, jack-rabbit; it is also used as a general name for pike.
The word "jack" is applied to mechanical devices and other objects smaller than the ordinary, or to appliances which take the place of manual labour. In the first class are the small object bowl in the game of bowls and jack rafters, those rafters in a building shorter than the main rafters. The jack as a ship's flag is always a smaller flag than the ensign. The jack is flown on a staff on the bowsprit of a vessel. In the British navy the jack is a small Union flag. (The Union flag should not be styled a Union Jack except when it is flown as a jack.) (See FLAG.) A more common use of "jack" is for various mechanical and other devices used as substitutes for men or boys. Thus the origin of the boot-jack and the meat-jack is explained. The New English Dictionary finds a transitional sense in the use of the - name "jack" for mechanical fig ures which strike the hours on a bell of a clock. Such a figure in the clock of St. Lawrence Church at Reading is called a jack in the parish accounts for There are many different applica tions of "jack" to certain levers and other parts of textile ma chinery; the principal mechanical application of the word, however, is to a portable hand-worked appliance for raising weights from below. Jacks range in
power from a few hundred weights to 500 tons ; the simple type is a crow-bar pivoted in an upright frame, giving a direct and rapid lift. To this simple pivoted lever have been added a screw turned by a tommy-bar, ratchet devices, pinion and rack, etc., for increasing power or rapidity of action ; and special forms have been evolved for use with motor cars, tram-cars, cable-drums, locomotives, railway and tram rails, ships, bridges, etc.
In most European languages the word "jack" in various forms appears for a short upper outer garment, particularly in the shape of a sleeveless (quilted) leather jerkin, sometimes with plates or rings of iron sewn to it. It was the common coat of defence of infantry in the middle ages. It was probably from some resemblance to the leather coat that the well-known leather vessels for holding liquor or for drinking were known as jacks. These drinking vessels, which are often of great size, were not described as black jacks till the 16th century, though known as jacks much earlier. About 1700 a jack of a different form, like an ordinary drinking mug with a tapering cylindrical body, often mounted in silver, came into vogue. The jack-boot, the heavy riding boot with long flap covering the knee and part of the thigh, and worn by troopers first during the 17th century, was so called probably from association with the leather jack or jerkin.