An Etymological Dictionary of Astronomy and Astrophysics

A Sudden, brief burst of light. In particular, → green flash.

Etymology (EN): From M.E. flasshen “to sprinkle, splash,” from flasken, probably imitative.

Etymology (PE): Deraxš, present stem of deraxšidan “to shine, radiate,” from raxš “lightening, reflection of light,” raxšidan “to shine, flash,” O.Pers. raucah-, Av. raocah- “light” (cf. Skt. roka- “brightness, light,” Gk. leukos “white, clear,” L. lux “light” (also lumen, luna), E. light, Ger. Licht, Fr. lumière;
PIE base *leuk- “light, brightness”); cognate with Mod.Pers. words
ruz “day,” rowšan “bright, clear,” foruq “light,” and afruxtan “to light, kindle.”