'electroshocker' is a compound formed from the prefix 'electro-' (from Greek 'ēlektron', meaning 'amber' and by extension 'electricity') and the English noun 'shocker' (from 'shock' + agent suffix '-er').

'electro-' entered English in scientific use via New Latin/Greek in the 19th century (related to 'electricity'), 'shock' comes from Old English/Old Germanic roots meaning a sudden blow or jolt; the compound 'electroshock' and related coinages arose in the 20th century with the development of electroconvulsive therapy, and 'electroshocker' developed as a term for devices that administer such shocks.

Originally, 'electro-' referred to amber or electric phenomena and 'shock' meant a sudden physical blow or jolt; combined, the modern sense became 'a device that delivers an electric jolt' and specifically names devices used for defense, control, or medical therapy.