The electron was named six years before anyone found it. When J. J. Thomson identified the particle in 1897, he did not even call it an electron.
The word belongs to George Johnstone Stoney, an Irish physicist. In 1891 he coined "electron" for a fixed unit of electric charge. He had inferred that unit from experiments that passed current through chemical solutions. It was a quantity, not yet a particle. Etymonline describes the coinage as "electric" plus "-on," the ending of "ion."
The deeper root is a piece of fossil resin. The Greek ēlektron meant "amber," and Homer, Hesiod and Herodotus all used it. It could also mean "pale gold," an alloy of roughly one part silver to four parts gold. Where the Greek word itself came from is unknown.
Amber mattered because of a simple trick. Rub it, and it pulls in small light things. In 1600 the English physician William Gilbert wrote De Magnete and apparently coined the Modern Latin electricus, "resembling amber." He used it for any substance that attracts other objects after rubbing. English "electric" followed in the 1640s, first used by Sir Thomas Browne.
Stoney's ending had its own short history. Michael Faraday introduced "ion" in 1834, on a suggestion from William Whewell. It is Greek for "going," since ions move toward an electrode.
Then came Thomson. His 1897 cathode-ray experiments convinced him that the rays were charged particles smaller than atoms. He called them "corpuscles." That same year George Francis FitzGerald suggested they were "free electrons." He meant the word in Joseph Larmor's sense, a structure in the ether, and was actually disagreeing with Thomson.
The physics settled over the following years, and Stoney's word won out over Thomson's. Today electron names the particle itself, not just its charge. Every electric current still carries, in its name, the memory of a polished lump of amber.