Etymology
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flash (n.2)
"sudden rush of water," 1660s, earlier "watery place or marsh, a swamp" (c. 1400; in place names from c. 1300), of uncertain origin or connection to flash (n.1); perhaps from Old French flache, from Middle Dutch vlacke. Flash flood is from 1940.
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flash (v.)
Middle English flashen, flasken (c. 1200), "sprinkle or splash (water, powder, etc.); to gush forth;" probably at least partly imitative (compare splash, dash), or in part from PIE *bhleu- "to swell, well up," extended form of root *bhel- (2) "to blow, swell." From c. 1400, of birds, "to dart or flit" also, of fire, "burst into flames." Some of the extended senses perhaps are from Scandinavian. Meanings "burst suddenly into view" (intransitive) and "emit or send forth suddenly" (transitive) are from 1580s. the Sense of "expose the genitals" is recorded by 1846. Related: Flashed; flashing. Flash card is from 1923.
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flash (n.1)
1560s, "sudden burst of flame or light," from flash (v.); originally of lightning. Figuratively (of wit, laughter, anger, etc.) from c. 1600. Meaning "period occupied by a flash, very short time" is from 1620s. Sense of "superficial brilliancy" is from 1670s. Meaning "first news report" is from 1857. The comic book character dates to 1940. Meaning "photographic lamp" is from 1913. Flash cube (remember those?) is from 1965.

Flash in the pan (1704 literal, 1705 figurative) is from old-style firearms, where the powder might ignite in the pan but fail to spark the main charge; hence figurative sense "brilliant outburst followed by failure."
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flash (adj.)
from flash (v.) in various and unconnected senses, often slang; sense of "of or associated with thieves, prostitutes, etc." is from c. 1700. That of "vulgar, showy" is from 1785 (it is older in flashy). That of "expert, smart" is from 1812.
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lamp (n.)

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."

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flash-point (n.)
also flashpoint, "temperature at which vapor will ignite momentarily," 1869, from flash (v.) + point (n.). Figurative use by 1955. Slightly earlier as flashing-point (1867).
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lamp-post (n.)
also lamppost, 1731, from lamp + post (n.1).
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lamp-black (n.)
pigment or ink made with pure, fine carbon, originally from the soot produced by burning oil in lamps, 1590s, see lamp (n.) + black (n.).
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