visible discharge of energy between cloud and cloud or cloud and ground, late Old English, "lightning, flash of lightning," verbal noun from lightnen "make bright," or else an extended form of Old English lihting, from leht (see light (n.)). The Old English word also meant "dawn, daybreak," and in Middle English "light of the sun, intense brightness, brilliance; the radiance of Christ." Another Middle English word for it was leven (mid-13c.), of uncertain origin, with no apparent source in Old English. (Old English had ligetung "lightning," from liget "lightning, flash of lightning." "Lightning" also was a specialized sense of lihting "lighting" and beorhtnes "brightness.")
Meaning "cheap, raw whiskey" is attested from 1781, also sometimes "gin." Lightning bug "firefly, phosphorescent beetle" is attested from 1778. Lightning rod from 1790.