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."
post n.1
"a timber of considerable size set upright," from Old English post "pillar, doorpost," and from Old French post "post, upright beam," both from Latin postis "door, post, doorpost," in Medieval Latin "a beam, rod, pole," which is perhaps from Vulgar Latin *por- "forth," a variant of pro- (see pro-) + stare "to stand" (from PIE root *sta- "to stand, make or be firm").
Similar compounds are Sanskrit prstham "back, roof, peak," Avestan parshti "back," Greek pastas "porch in front of a house, colonnade," Middle High German virst "ridgepole," Lithuanian pirštas, Old Church Slavonic pristu "finger" (PIE *por-st-i-).
Later also of metal. As a type of hardness, lifelessness, deafness by early 15c.