Etymology
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tough (adj.)
Old English toh "strong and firm in texture, tenacious, sticky," from Proto-Germanic *tanhu- (source also of Middle Low German tege, Middle Dutch taey, Dutch taai, Old High German zach, German zäh), which Watkins suggests is from PIE *denk- "to bite," from the notion of "holding fast." See rough for spelling change.

From c. 1200 as "strong, powerful;" c. 1300 as "not tender or fragile;" early 14c. as "difficult to chew," also "hard to endure." Figurative sense of "steadfast" is mid-14c.; that of "hard to do, trying, laborious" is from 1610s. Verb tough it "endure the experience" is first recorded 1830, American English. Tough guy attested from 1901. Tough-minded first recorded 1907 in William James. Tough luck first recorded 1912; tough shit, dismissive retort to a complaint, is from 1946.
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creek (n.)

mid-15c., creke "narrow inlet in a coastline," altered from kryk (early 13c.; in place names from 12c.), probably from Old Norse kriki "corner, nook," perhaps influenced by Anglo-French crique, itself from a Scandinavian source via Norman. Perhaps ultimately related to crook and with an original notion of "full of bends and turns" (compare dialectal Swedish krik "corner, bend; creek, cove").

Extended to "inlet or short arm of a river" by 1570s, which probably led to use for "small stream, brook" in American English (1620s). In U.S. commonly pronounced and formerly sometimes spelled crick. Also used there and in Canada, Australia, New Zealand for "branch of a main river," possibly from explorers moving up main rivers and seeing and noting mouths of tributaries without knowing they often were extensive rivers of their own.

Slang phrase up the creek "in trouble" (often especially "pregnant") is attested by 1941, perhaps originally armed forces slang for "lost while on patrol," or perhaps a cleaned-up version of the older up shit creek in the same sense.

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pot (n.1)

"deep, circular vessel," from late Old English pott and Old French pot "pot, container, mortar" (also in erotic senses), both from a general Low Germanic (Old Frisian pott, Middle Dutch pot) and Romanic word from Vulgar Latin *pottus, which is of uncertain origin, said by Barnhart and OED to be unconnected to Late Latin potus "drinking cup." Similar Celtic words are said to be borrowed from English and French.

Specifically as a drinking vessel from Middle English. Slang meaning "large sum of money staked on a bet" is attested from 1823; that of "aggregate stakes in a card game" is from 1847, American English.

Pot roast "meat (generally beef) cooked in a pot with little water and allowed to become brown, as if roasted," is from 1881. Pot-plant is by 1816 as "plant grown in a pot." The phrase go to pot "be ruined or wasted" (16c.) suggests cooking, perhaps meat cut up for the pot. In phrases, the pot calls the kettle black-arse (said of one who blames another for what he himself is also guilty of) is from c. 1700; shit or get off the pot is traced by Partridge to Canadian armed forces in World War II. To keep the pot boiling "provide the necessities of life" is from 1650s.

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sad (adj.)

Old English sæd "sated, full, having had one's fill (of food, drink, fighting, etc.), weary of," from Proto-Germanic *sathaz (source also of Old Norse saðr, Middle Dutch sat, Dutch zad, Old High German sat, German satt, Gothic saþs "satiated, sated, full"), from PIE *seto-, from root *sa- "to satisfy." Related: Sadder; saddest.

In Middle English and into early Modern English the prevailing senses were "firmly established, set; hard, rigid, firm; sober, serious; orderly and regular," but these are obsolete except in dialect. The sense development seems to have been via the notion of "heavy, ponderous" (i.e. "full" mentally or physically), thus "weary, tired of." By c. 1300 the main modern sense of "unhappy, sorrowful, melancholy, mournful" is evident. An alternative course would be through the common Middle English sense of "steadfast, firmly established, fixed" (as in sad-ware "tough pewter vessels") and "serious" to "grave." In the main modern sense, it replaced Old English unrot, negative of rot "cheerful, glad."

By mid-14c. as "expressing or marked by sorrow or melancholy." The meaning "very bad, wicked" is from 1690s, sometimes in jocular use. Slang sense of "inferior, pathetic" is from 1899; sad sack is 1920s, popularized by World War II armed forces (specifically by cartoon character invented by Sgt. George Baker, 1942, and published in U.S. Armed Forces magazine "Yank"), probably a euphemistic shortening of the common military slang phrase sad sack of shit.

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four (adj., n.)

"1 more than three, twice two; the number which is one more than three; a symbol representing this number;" Old English feower "four; four times," from Proto-Germanic *fedwores (source also of Old Saxon fiuwar, Old Frisian fiower, fiuwer, Frankish *fitter-, Dutch vier, Old High German fior, German vier, Old Norse fjorir, Danish fire, Swedish fyra, Gothic fidwor "four"), from PIE root *kwetwer- "four." The phonetic evolution of the Germanic forms has not been fully explained; Watkins explains the -f- as being from the following number (Modern English five).

To be on all fours is from 1719; earlier on all four (14c.). Four-letter word as a euphemism for one of the short words generally regarded as offensive or objectionable is attested from 1923; four-letter man is recorded from 1920 (apparently as a euphemism for a shit). Compare Latin homo trium litterarum, literally "three-letter man," a euphemism for fur "a thief." A four-in-hand (1793) was a carriage drawn by four horses driven by one person; in the sense of "loosely tied necktie" it is attested from 1892. To study The History of the Four Kings (1760, compare French Livres des Quatre Rois) contains an old euphemistic slang phrase for "a pack of cards," from the time when card-playing was considered a wicked pastime for students. Slang 4-1-1 "essential information" (by 1993) is from the telephone number called to get customer information. The four-color problem so called from 1879. The four-minute mile was attained 1954.

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shoot (v.)

Old English sceotan "to hurl missiles, cast; strike, hit, push; run, rush; send forth swiftly; wound with missiles" (class II strong verb; past tense sceat, past participle scoten), from Proto-Germanic *skeutanan (source also of Old Saxon skiotan, Old Norse skjota "to shoot with (a weapon); shoot, launch, push, shove quickly," Old Frisian skiata, Middle Dutch skieten, Dutch schieten, Old High German skiozan, German schießen), from PIE root *skeud- "to shoot, chase, throw."

In reference to pool playing, from 1926. Meaning "to strive (for)" is from 1967, American English. Sense of "descend (a river) quickly" is from 1610s. Meaning "to inject by means of a hypodermic needle" is attested from 1914. Meaning "photograph" (especially a movie) is from 1890. As an interjection, an arbitrary euphemistic alteration of shit, it is recorded from 1934.

Shoot the breeze "chat" is attested by 1938 (as shooting the breeze), perhaps originally U.S. military slang. Shoot-'em-up (adj.) in reference to violent entertainment (Western movies, etc.) is from 1942. Shoot to kill is attested from 1867. Shoot the cat "to vomit" is from 1785. To shoot the moon originally meant "depart by night with ones goods to escape back rent" (c. 1823).

O, 'tis cash makes such crowds to the gin shops roam,
And 'tis cash often causes a rumpus at home ;
'Tis when short of cash people oft shoot the moon ;
And 'tis cash always keeps our pipes in tune.
Cash! cash! &c.
["The Melodist and Mirthful Olio, An Elegant Collection of the Most Popular Songs," vol. IV, London, 1829]
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