rock (n.1)

[stone, mass of mineral matter], Middle English rokke, roche "stone as a substance; large rocky formation, rocky height or outcrop, crag," from Old English rocc (as in stanrocc "stone rock or obelisk") and directly from Old North French roque, variant of Old French roche, which is cognate with Medieval Latin rocca (8c.), from Vulgar Latin *rocca, a word of uncertain origin. According to Klein and Century Dictionary, sometimes said to be from Celtic (compare Breton roch). Diez suggests Vulgar Latin *rupica, from Latin rupes "rocks."

In Middle English it seems to have been used principally for large rock formations but occasionally of individual boulders. The extended sense of "a stone of any size" is by 1793, American English colloquial, and long was considered incorrect.

It is an error to use rock for a stone so small that a man can handle it : only a fabulous person or a demi-god can lift a rock. [Century Dictionary]

The meaning "precious stone," especially a diamond, is by 1908, U.S. slang; the sense of "crystallized cocaine" is attested from 1973 in West Coast slang. Also used attributively in names of animals that frequent rocky habitats, as in rockfish, rock badger, rock lobster (the last attested by 1843).

Rock is used figuratively for "a sure foundation, something which gives one protection and security" (especially with reference to Christ), from the 1520s (Tyndale); but it also has been used since the 1520s as "cause or source of peril or destruction," an image from shipwrecks.

Between a rock and a hard place "beset by difficulties with no good alternatives" is attested by 1914 in U.S. Southwest:

to be between a rock and a hard place, vb. ph. To be bankrupt. Common in Arizona in recent panics; sporadic in California. [Dialect Notes, vol. v, part iv, 1921]
As an example of fine distinctions, a party of men were discussing the present situation of the German army, this week. One remarked that the Germans were between the devil and the deep sea; while another corrected him by saying that the Germans were between the upper and nether mill stone. The third man whose name is Pilgreen, and who works in the treasurer's office, simply remarked that the Germans were between a rock and a hard place. [local item in the Pouteau (Oklahoma) Weekly Sun,  Oct. 1, 1914]

The rock-scissors-paper game is attested by that name by 1976 (as paper stone and scissors by 1941). Sources agree it is based on Japanese Jan Ken Po or Jan Ken Pon (or Janken for short); the Japanese game is described in English publications by 1879.

Related entries & more 
line (n.)

a Middle English merger of Old English line "cable, rope; series, row, row of letters; rule, direction," and Old French ligne "guideline, cord, string; lineage, descent" (12c.), both from Latin linea "linen thread, string, plumb-line," also "a mark, bound, limit, goal; line of descent," short for linea restis "linen cord," and similar phrases, from fem. of lineus (adj.) "of linen," from linum "linen" (see linen).

The earliest sense in Middle English was "cord used by builders for taking measurements;" extended late 14c. to "a thread-like mark" (from sense "cord used by builders for making things level," mid-14c.), also "track, course, direction." Meaning "limit, boundary" (of a county, etc.) is from 1590s. The mathematical sense of "length without breadth" is from 1550s. From 1530s as "a crease of the face or palm of the hand." From 1580s as "the equator."

Sense of "things or people arranged in a straight line" is from 1550s. Now considered American English, where British English uses queue (n.), but the sense appears earliest in English writers. Sense of "chronologically continuous series of persons" (a line of kings, etc.) is from late 14c.

Meaning "one's occupation, branch of business" is from 1630s, according to OED probably from misunderstood KJV translation of II Corinthians x.16, "And not to boast in another mans line of things made ready to our hand," where line translates Greek kanon which probably meant "boundary, limit;" the phrase "in another man's line" being parenthetical.

Commercial meaning "class of goods in stock" is from 1930, so called from being goods received by the merchant on a line in the specific sense "order given to an agent" for particular goods (1834). Insurance underwriting sense is from 1899. Line of credit is from 1958.

Meaning "series of public conveyances" (coaches, later ships) is from 1786; meaning "continuous part of a railroad" is from 1825. Meaning "telegraph wire between stations" is from 1847 (later "telephone wire"). Meaning "cord bearing hooks used in fishing" is from c. 1300. Meaning "policy or set of policies of a political faction" is 1892, American English, from notion of a procession of followers; this is the sense in the political party line, and, deteriorated, it is the slang line that means "glib and plausible talk meant to deceive."

In British army, the Line (1802) is the regular, numbered troops, as distinguished from guards, auxiliaries, militia, etc. In the Navy (1704) it refers to the battle line (the sense in ship of the line, which is attested from 1706).

Dutch lijn, Old High German lina, German Leine, Old Norse lina "a cord, rope," are likewise from Latin. Spanish and Italian have the word in the learned form linea. In continental measurements, a subdivision of an inch (one-tenth or one-twelfth in England), attested in English from 1660s but never common. Also see lines.

To get a line on "acquire information about" is from 1903. To lay it on the line is from 1929 as "to pay money;" by 1954 as "speak plainly." End of the line "as far as one can go" is from 1948. One's line of work, meaning "pursuit, interest" is from 1957, earlier line of country (1861). Line-drawing is from 1891. A line-storm (1850) is a type supposed to happen in the 10 days or two weeks around the times the sun crosses the equator.

Related entries & more 

Page 38