Old English clingan "hold fast, adhere closely; congeal, shrivel" (strong verb, past tense clang, past participle clungen), from Proto-Germanic *klingg- (source also of Danish klynge "to cluster;" Old High German klinga "narrow gorge;" Old Norse klengjask "press onward;" Danish klinke, Dutch klinken "to clench;" German Klinke "latch").
The main sense shifted in Middle English to "adhere to" (something else), "stick together." Of persons in embrace, c. 1600. Figuratively (to hopes, outmoded ideas, etc.), from 1580s. Of clothes from 1792. Related: Clung; clinging.
Old English stan, used of common rocks, precious gems, concretions in the body, memorial stones, from Proto-Germanic *stainaz (source also of Old Norse steinn, Danish steen, Old Saxon sten, Old Frisian sten, Dutch steen, Old High German stein, German Stein, Gothic stains), from PIE *stoi-no-, suffixed form of root *stai- "stone," also "to thicken, stiffen" (source also of Sanskrit styayate "curdles, becomes hard;" Avestan stay- "heap;" Greek stear "fat, tallow," stia, stion "pebble;" Old Church Slavonic stena, Russian stiena "wall").
Sense of "testicle" is from late Old English. The British measure of weight (usually equal to 14 pounds) is from late 14c., originally a specific stone. Stone-fruit, one with a pit, is from 1520s. Stone's throw for "a short distance" is attested from 1580s. Stone Age is from 1864. To kill two birds with one stone is first attested 1650s. To leave no stone unturned is from 1540s.
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Definitions of clingstone from WordNet
fruit (especially peach) whose flesh adheres strongly to the pit;