word-forming element, in English meaning usually "out of, from," but also "upwards, completely, deprive of, without," and "former;" from Latin ex "out of, from within; from which time, since; according to; in regard to," from PIE *eghs "out" (source also of Gaulish ex-, Old Irish ess-, Old Church Slavonic izu, Russian iz). In some cases also from Greek cognate ex, ek. PIE *eghs had comparative form *eks-tero and superlative *eks-t(e)r-emo-. Often reduced to e- before -b-, -d-, -g-, consonantal -i-, -l-, -m-, -n-, -v- (as in elude, emerge, evaporate, etc.).
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."