c. 1200, "vessel containing flammable liquid and a wick to lift it by capillary action when lit," from Old French lampe "lamp, lights" (12c.), from Latin lampas "a light, torch, flambeau," from Greek lampas "a torch, oil-lamp, beacon-light, light," from lampein "to shine," perhaps from a nasalized form of PIE root *lehp- "to light, glow" (source also of Lithuanian lopė "light," Hittite lappzi "to glow, flash," Old Irish lassar "flame," Welsh llachar "glow").
Replaced Old English leohtfæt "light vessel." From 19c. in reference to gas and later electric lamps. To smell of the lamp "be a product of laborious night study," said disparagingly of a literary work, is attested from 1570s (compare midnight oil). The Greek stem lampad- formed a number of compounds, some in English, such as lampadomancy (1650s) "divination from variations in the flame of a lamp."
Variant lanthorn (16c.-19c.) was folk etymology based on the common use of horn as a translucent cover. Lantern-jaws "hollow, long cheeks" is from a resemblance noted at least since mid-14c.; Johnson suggests the idea is "a thin visage, such as if a candle were burning in the mouth might transmit the light."