electron

Coined in 1891 by Anglo-Irish scientist George Stoney as a blend of electric and ion, after he'd tried out electrine (as early as 1874) and electrolion before settling on this form.

Stoney originally meant it for the electric charge carried by a univalent ion, not a particle. When the particle itself was discovered in 1896, a rival name, electrion, was floated in 1906 but dropped once Hendrik Lorentz favored electron instead.

It's built from electro- plus the suffix -on, the same ending pattern later particle names would borrow.