The word aventurine belongs first to glass, not stone. Italian glassmakers, traditionally associated with Murano, produced a copper flecked amber or brown glass, still sold today as goldstone, in which tiny metallic copper crystals precipitate through the glass and catch the light. The traditional account, that the effect was found by accident when copper filings fell into a batch of molten glass, is the kind of origin story glassmaking history often cannot fully verify, but the name it left behind is not in dispute: aventurine, from the Italian a ventura, by chance, records the accident whether or not the specific tale is exactly true.
The name only reached the mineral afterward, and it reached it because of a resemblance rather than a shared cause. Natural quartzite showing a similar internal shimmer, called aventurescence, was named after the glass it visually resembled, even though the two effects come from entirely different physical sources: metallic copper crystals suspended in glass on one hand, and flat, reflective flakes of mica, commonly the chromium bearing variety fuchsite in the green stone, embedded between quartz grains on the other. Green aventurine's color is fuchsite's own green, not a property of the quartz itself, which is why aventurine occurs in other colors, blue, orange, red, wherever a different platy mineral supplies the sparkle instead. One name, two unrelated mechanisms, joined only by the accident of how each one looks.
Sources Mindat.org - The Mineralogical ReferenceHudson Institute of Mineralogy with The Oxford English Dictionary, 3rd editionOxford University Press