masc. proper name, attested by 1218, probably via Anglo-French Jake, Jaikes, from Old French Jacques (which was a diminutive of Latin Jacobus; see Jacob), but in English the name always has been regarded as a familiar form of John, and some have argued that it is a native formation. In Middle English spelled Jakke, Jacke, etc., and pronounced as two syllables ("Jackie").
In England, Jack became a generic name applied familiarly or contemptuously to anybody (especially a young man of the lower classes) from late 14c. Later used especially of sailors (1650s; Jack-tar is from 1781); Jack-ashore (adj.) "drinking and in high spirits, recklessly spending" (1875) also is an image from sailors (1840 as a book title). In U.S., as a generic name addressed to an unknown stranger, attested from 1889. Every man Jack "everyone" is from 1812. Also see jack (n.).
Used in male personifications from 15c.; first record of jack-of-all-trades "person handy at any kind of work or business" is from 1610s; Jack Frost is from 1826; Jack-nasty "a sneak or sloven" is from 1833 (Jack-nasty-face, a sea-term for a common sailor, is from 1788). Jack Sprat for a small, light man is from 1560s (his opposite was Jack Weight). Jack-pudding "comical clown, buffoon" is from 1640s. Jack-Spaniard is from 1703 as a Spaniard, 1833 as "a hornet" in the West Indies. Other personifications listed in Farmer & Henley include jack-snip "a botching tailor," Jack-in-office "overbearing petty official" (1680s), Jack-on-both-sides "a neutral," Jack-out-of-doors "a vagrant" (1630s), jack-sauce "impudent fellow" (1590s).
The U.S. plant jack-in-the-pulpit (Indian turnip) is attested by 1833. Jack the Ripper was active in London 1888. The Scottish form is Jock (compare jockey (n.)). Alliterative coupling of Jack and Jill is from 15c. (Iakke and Gylle, Ienken and Iulyan). Jack Ketch for "hangman, executioner" (1670s) is said to be from the name of a public executioner in the time of James II (compare Derrick); it also was used as a verb meaning "to hang."
Old English lagu (plural laga, combining form lah-) "ordinance, rule prescribed by authority, regulation; district governed by the same laws;" also sometimes "right, legal privilege," from Old Norse *lagu "law," collective plural of lag "layer, measure, stroke," literally "something laid down, that which is fixed or set."
Rare in Old English, it ousted the more usual ae and also gesetnes, which also were etymologically "something placed or set."
In physics, "a proposition which expresses the regular order of things," from 1660s. Law and order have been coupled since 1796. To lay down the law (1752) is pleonastic (the "law" in the figure is biblical law, laid down from the pulpit). Poor laws provided for the support of paupers at public expense; sumptuary laws restrained excesses in apparel, food, or luxuries.
It is more common for Indo-European languages to use different words for "a specific law" and for "law" in the general sense of "institution or body of laws," for example Latin lex "a law," ius "a right," especially "legal right, law."
Indo-European words for "a law" are most commonly from verbs for "to put, place, set, lay," such as Greek thesmos (from tithemi "to put, place"), Old English dom (from PIE *dhe- "to put, place, set"), Lithuanian įstatymas (from statyti "cause to stand, set up, establish"), Polish ustawa (from stać "stand"). Also compare Old English gesetnes (above), statute, from Latin statuere; German Gesetz "a law, statute," from Old High German gisatzida "a fixing, determination, assessment," with sezzen (modern German setzen) "to make sit, set, put."
Words for "law" in the general sense mostly mean etymologically "what is right" and often are connected with adjectives for "right" (themselves often figurative uses of words for "straight," "upright," "true," "fitting," or "usage, custom." Such are Greek nomos (as in numismatic); French droit, Spanish derecho, from Latin directus; Polish prawo, Russian pravo (from Old Church Slavonic pravŭ "straight," in the daughter languages "right"); also Old Norse rettr, Old English riht, Dutch recht, German Recht (see right (adj.1)).
[L]earn to obey good laws before you seek to alter bad ones [Ruskin, "Fors Clavigera"]