tombstone n.

c. 1200, tumbe, early 14c. tomb, from Anglo-French tumbe and directly from Old French tombe "tomb, monument, tombstone" (12c.), from Late Latin tumba (also source of Italian tomba, Spanish tumba), from Greek tymbos "mound, burial mound," generally "grave, tomb."

Watkins suggests it is perhaps from PIE root *teue- "to swell," but Beekes writes that it is probably a Pre-Greek (non-IE) word. He writes that Latin tumulus "earth-hill" and Armenian t'umb "landfill, earthen wall" "may contain the same Pre-Greek/Mediterranean word," and suggests further connections to Middle Irish tomm "small hill," Middle Welsh tom "dung, mound."

The final -b began to be silent about the time of the spelling shift (compare lamb, dumb). Modern French tombeau is from Vulgar Latin diminutive *tumbellus. The Tombs, slang for "New York City prison" is recorded from 1840.

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.