is from 15c. (Ienken and Iulyan). As a generic name addressed to an unknown stranger, it is attested from 1889 in Amer.Eng. Used especially of sailors (1659; Jack-tar is from 1781).
late 14c., jakke "a mechanical device," from the name Jack
. Used by 14c. for "any common fellow" (mid-14c.), and thereafter extended to various appliances replacing servants (1570s). Used generically of men (jack-of-all-trades, 1610s), male animals (1620s, see jackass, jackdaw,
etc.), and male personifications (1520s, e.g. Jack Frost). The jack in a pack of playing cards (1670s) is in Ger. Bauer "peasant." Jackhammer is from 1930. Jack shit "nothing at all" is 1970s southern U.S. student slang. The jack of Union Jack
is a nautical term for a small flag at the bow of a ship (1630s).
1873, jack up, originally "abandon, give up," later (1885) "hoist with a jack;" then "increase prices, etc." (1904, Amer.Eng.), all from the noun. Jack off (v.) "to masturbate" is attested from 1916, probably from jack in the sense of "penis."
1835, from earlier Lynch law (1811), likely named after William Lynch (1742-1820) of Pittsylvania, Va., who c.1780 led a vigilance committee to keep order there during the Revolution. Other sources trace the name to Charles Lynch (1736-1796) a Virginia magistrate who fined and imprisoned Tories in his
district c.1782, but the connection to him is less likely. Originally any sort of summary justice, especially by flogging; narrowing of focus to "extralegal execution by hanging" is 20c. Lynch mob is attested from 1838. The surname is either from O.E. hlinc "hill" or Ir. Loingseach "sailor." Cf. earlier Lydford law, from a place in Dartmoor, England, "where was held a Stannaries Court of summary jurisdiction" [Weekley], hence:
"Lydford law: is to hang men first, and indite them afterwards." [Thomas Blount, "Glossographia," 1656]