jolt (n.)

1590s, "a knock," from jolt (v.). Meaning "a jarring shock" is from 1630s.

jolt (v.)

1590s (transitive), perhaps from Middle English jollen, chollen "to knock, to batter" (early 15c.), or an alteration of obsolete jot (v.) "to jostle" (1520s). Perhaps related to earlier jolt head "a big, stupid head" (1530s). Intransitive sense from 1703. Figurative sense of "to startle, surprise" is from 1872. Related: Jolted; jolting.