From the Online Etymology Dictionary
Comments in red italics by Wes Clark
Rugby - 1864, after Rugby, public school where the game was played, from city of Rugby in Warwickshire, central England. The place name is Rocheberie (1086) "fortified place of a man called "Hroca," second element from O.E. burh (dat. byrig), replaced by 13c. with O.N. -by "village." First element perhaps rather O.E. hroc "rook." Rugby Union formed 1871. Slang rugger for "rugby player" is from 1893. (Stating that one plays rugby is a whole lot more macho than stating that one plays rocheberie.)
Scrum - 1888, abbreviation of scrummage, a variant form of scrimmage (q.v.).
Scrimmage - c.1470, alteration of skirmish (q.v.). The verb is recorded from 1825. Meaning in rugby and U.S. football dates from 1857, originally "a confused struggle between players."
Skirmish - c.1300, from O.Fr. escarmouche "skirmish," from It. scaramuccia, probably from a Gmc. source (cf. O.H.G. skirmen "to protect, defend"), influenced in M.E. by a separate verb skirmysshen "to brandish a weapon," from O.Fr. eskirmiss-, stem of eskirmir "to fence," from Frankish *skirmjan, from the same Gmc. source. The verb is attested from c.1470. Cf. also scrimmage. (So, “scrum” is short for “scrummage,” which is variant form of “scrimmage,” which is derived from “skirmish.” Even dogs can figure that one out – I notice sometimes they start barking, thinking a fight is going on, when they see a scrum.)
Redshirt (v.) “To withdraw (a player) from the varsity team to add a year to his or her eligibility," 1955, in allusion to the red shirts worn by athletes on the scrimmage squad.
Motley - c.1386, from Anglo-Fr. motteley, probably from O.E. mot "speck." "Diversified in color," especially of a fool's dress. Hence, allusively, "a fool" (1600). (Not the only time we’ll see a connection between rugby and idiocy, I suspect.)
Soccer - 1889, socca, later socker (1891), soccer (1895), originally university slang, from a shortened form of Assoc., abbreviation of association in Football Association (as opposed to Rugby football); cf. rugger, but they hardly could have taken the first three letters of Assoc. (Oh, I don’t know…)
Forward - O.E. foreweard "toward the front," from fore + -ward. The verb is first recorded 1596. Sense of "early" is from 1526; that of "presumptuous" is attested from 1561. The position in football so called since 1879. British Eng. until mid-20c. preserved the distinction between forward and forwards, the latter expressing "a definite direction viewed in contrast with other directions." In Amer.Eng., however, forward prevails in all senses since Webster (1832) damned forwards as "a corruption." (Bar owners and backline players probably hold the same opinion.)
Back - O.E. bæc "back, backwards, behind," from P.Gmc. *bakam (cf. O.S., M.Du. bak, O.Fris. bek), which mostly has been ousted in other modern Gmc. languages by words akin to Mod.E. ridge. Verb "to move (something) back" is from 1486; meaning "to support" (as by a bet) is first attested 1548. Backbiting is first recorded c.1175; backslide in the religious sense is from 1581; backwoods is from 1709. Back-date first recorded 1946. Backside "rump" is first recorded 1500. Back door "devious, shady, illegal" is from 1643. The verb back off "retreat" is attested from 1930s. Back down in fig. sense of "withdraw a charge" is first attested 1859, Amer.Eng., from notion of descending a ladder, etc. Back-firing "premature ignition in an internal-combustion engine" is first recorded 1897. Back-stabber in the fig. sense is from 1906. Back-seat driver first attested 1926. Back-track "retrace one's steps" is from 1904. Back-to-nature (adj.) is first attested 1915. Backpack is 1914 as a noun, 1916 as a verb. The back of (one's) hand has been used to imply contempt and rejection since at least 1300; to know something like the back of one's hand, implying familiarity, is first attested 1943. Back bench in the House of Commons sense is from 1874. Back-hand as a tennis stroke dates from 1657. Back-talk "impertinent retort" is first recorded 1858, originally often used in literary attempts at low Irish idiom. To be on the back burner in the figurative sense is from 1960. Back-formation coined by Eng. lexicographer James Murray (1837-1915). (I think the meanings "rump, devious, shady, illegal" are especially appropriate for this rugby term.)
Pack (v.) - c.1300, "to put together in a pack," from pack (n.), possibly influenced by Anglo-Fr. empaker (1294) and M.L. paccare "pack." Some senses suggesting "make secret arrangement" are from an Elizabethan mispronunciation of pact. Sense of "to carry or convey in a pack" (1805) led to general sense of "to carry in any manner;" hence to pack heat "carry a gun," underworld slang from 1940s; "to be capable of delivering" (a punch, etc.) is from 1921. (Yes, I do believe a rugby pack is capable of delivering a punch.)
Pack (n.) - "bundle," c.1225, probably from a Low Ger. word (cf. M.Du. pac, pack "bundle," M.L.G. pak, M.Flem. pac, attested from 1199), originally a term of wool traders in Flanders; or possibly from O.N. pakki, all of unknown origin. It. pacco is a Du. loan word. Meaning "set of persons" (usually of a low character" is c.1300, older than sense of "group of hunting animals" (early 15c.). Extended to collective sets of playing cards (1597), floating ice (1791), cigarettes (1924), and submarines (1943). Meaning "knapsack on a frame" is attested from 1916. Pack-horse is from c.1475; packsaddle "saddle for supporting packs on the back of a mount" is from 1388 (pakke sadil). Pack of lies first attested 1763. (A set of persons of low character – heh.)
Tackle (v.) - 1340, "entangle, involve," from tackle (n.). Sense of "to furnish (a ship) with tackles" is from c.1400; meaning "to harness a horse" is recorded from 1714. The meaning "lay hold of, come to grips with, attack" is attested from 1828, described by Webster that year as "a common popular use of the word in New England, though not elegant;" fig. sense of "try to deal with" (a task or problem) is from 1840. The verb in the sporting sense first recorded 1884.
Tackle (n.) - c.1250, "apparatus, gear," from M.Du. or M.L.G. takel "the rigging of a ship," perhaps related to M.Du. taken "grasp, seize" (see take), or perhaps from root of tack (1). Meaning "apparatus for fishing" is recorded from 1398. The noun meaning "act of tackling" in the sporting sense is recorded from 1876 (see tackle (v.)); as the name of a position in Amer. football, it is recorded from 1891.
Touchdown - 1864, from touch (v.) + down (adv.). Originally in rugby, where the ball is lit. touched down on the other side of the goal.
Hat trick - c.1877, originally from cricket, "taking three wickets on three bowls;" extended to other sports (esp. ice hockey) c.1909. Allegedly because it entitled the bowler to receive a hat from his club commemorating the feat (or entitled him to pass the hat for a cash collection), but also infl. by the image of a conjurer pulling things from his hat (though hat trick in this sense is not attested until 1886).
Hooker - "Prostitute," often traced to the disreputable morals of the Army of the Potomac (American Civil War) under the tenure of Gen. "Fighting Joe" Hooker (1863), and the word probably was popularized by this association at that time. But it is said to have been in use in North Carolina c.1845 ("If he comes by way of Norfolk he will find any number of pretty Hookers in the Brick row not far from French's hotel."). One theory traces it to Corlear's Hook, a disreputable section of New York City. Perhaps related to hooker "thief, pickpocket" (1567), but most likely an allusion to prostitutes hooking or snaring clients. Hook in the figurative sense of "that by which anyone is attracted or caught" is recorded from 1430; and hook (v.) in the figurative sense of "catch hold of and draw in" is attested from 1577; in reference to "fishing" for a husband or a wife, it was in common use from c.1800. All of which makes the modern sense seem a natural step. The family name Hooker (attested from c.975 C.E.) would mean "maker of hooks," or else refer to an agricultural laborer who used a hook (cf. O.E. weodhoc "weed-hook").
Prop (n.1) - "Support," 1440, from M.Du. proppe "vine prop, support," of unknown origin. Related to O.H.G. pfropfo, Ger. pfropfen "to prop," perhaps from L. propago "a set, layer of a plant" (see propagation). Ir. propa, Gael. prop are from English. The verb meaning "to support" is attested from 1492. (“Vine support”: I might have known that the word originally had something to do with alcohol…)