Is it ensure, insure, or assure?
"stone, mass of mineral matter," c.1300, from Old English rocc (e.g. stanrocc "stone rock or obelisk") and directly from Old North French roque, which is cognate with Medieval Latin rocca (8c.), from Vulgar Latin *rocca, of uncertain origin, according to Klein sometimes said to be from Celtic (cf. Breton roch).
In Middle English it seems to have been used principally for rock formations as opposed to individual stones. Meaning "precious stone, especially a diamond," is 1908, U.S. slang. Meaning "crystallized cocaine" is attested from 1973, in West Coast U.S. slang. Figurative use for "sure foundation" (especially with reference to Christ) is from 1520s; but also from 1520s as "source of danger or destruction," in reference to shipwrecks (e.g. on the rocks). Also used attributively in names of animals that frequent rocky habitats, e.g. rock lobster (1843). Between a rock and a hard place first attested 1921:
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]Rock-ribbed is from 1776, originally of land; figurative sense of "resolute" first recorded 1887. Rock-happy (1945) was U.S. Pacific Theater armed forces slang for "mentally unhinged after too much time on one island." The rock-scissors-paper game is attested by that name from 1976; from 1968 as paper-stone-scissors. A 1967 source says it is based on Japanese Jan Ken Pon (or Janken for short), which is said to mean the same thing more or less.
"to sway," late Old English roccian "move a child gently to and fro," related to Old Norse rykkja "to pull, tear, move," Swedish rycka "to pull, pluck," Middle Dutch rucken, Old High German rucchan, German rücken "to move jerkily."
Meaning "cause to sway back and forth" is from late 13c. Intransitive sense from late 14c. For popular music senses, see rock (v.2). Related: Rocked; rocking. To rock the boat in the figurative sense "stir up trouble" is from 1914. Rock-a-bye first recorded 1805 in nursery rhyme.
"to dance to popular music with a strong beat," 1948 (first attested in song title "We're gonna rock"), from rock (v.1), in earlier blues slang sense of "to cause to move with musical rhythm" (1922); often used at first with sexual overtones (cf. 1922 song title "My Man Rocks Me (with One Steady Roll)"). Sense developed early 1950s to "play or dance to rock and roll music." Related: Rocked; rocking. Rocksteady, Jamaican pop music style (precursor of reggae), is attested from 1969.
Rock (rŏk), John. 1890-1984.
American gynecologist and obstetrician who helped develop (1954) the first effective oral contraceptive.
(Heb. tsur), employed as a symbol of God in the Old Testament (1 Sam. 2:2; 2 Sam. 22:3; Isa. 17:10; Ps. 28:1; 31:2,3; 89:26; 95:1); also in the New Testament (Matt. 16:18; Rom. 9:33; 1 Cor. 10:4). In Dan. 2:45 the Chaldaic form of the Hebrew word is translated "mountain." It ought to be translated "rock," as in Hab. 1:12 in the Revised Version. The "rock" from which the stone is cut there signifies the divine origin of Christ. (See STONE.)