gemstone (n.)

"a precious stone" (especially when cut or polished), c. 1300, probably from Old French gemme (12c.), from Latin gemma "precious stone, jewel," originally "bud," from Proto-Italic *gebma- "bud, sprout," from PIE *geb-m- "sprout, bud" (source also of Lithuanian žembėti "to germinate, sprout," Old Church Slavonic prozebnoti "to germinate").

The two competing traditional etymologies trace it either to the root *gembh- "tooth, nail" [Watkins] or *gem- "'to press." De Vaan finds the second "semantically unconvincing" and leans toward the first despite the difficult sense connection.

Of persons, "a rare or excellent example (of something)" from late 13c. Alternative forms iemme, gimme persisted into 14c. and might represent a survival of Old English gimm "precious stone, gem, jewel," also "eye," which was borrowed directly from Latin gemma.

"discrete piece of rock," especially not a large one, Old English stan, which was 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).

This is reconstructed to be 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").

From late 12c. as "substance of which stones consist, rock, stone as a medium." The sense of "testicle" was in late Old English. The British measure of weight (usually equal to 14 pounds) is from late 14c., originally a specific stone.

Stone-fruit, "drupe, fruit with a hard stone or nut at the center," is from 1520s. Stone's throw for "a short distance" is attested from 1580s; stone's cast in the same sense is from late 13c., also "a short time." Stone age, "period of human cultural development marked by tools or weapons made of stone," is from 1864; adjectival extended sense of "outmoded, unsophisticated" is by 1927.

To kill two birds with one stone "accomplish two purposes with one act" is attested by 1650s. To leave no stone unturned "use every possible expedient" is from 1540s. To have a heart of stone figuratively is by late 14c.