Blush
Old English blyscan ; related to modern Dutch blozen .
wiktionary
From Middle English blusshen, bluschen, blusschen, blisshen, from Old English blysċan(“to be red; shine”), perhaps from Proto-Germanic *blaskijaną, from *blasǭ(“burning candle; torch”) or alternatively from Proto-Germanic *bluskijaną, from *blusjǭ(“torch”). Cognate with Middle Low German blöschen(“to blush”). Compare also Old English blysian(“to burn; blaze”), Dutch blozen(“to blush”), Danish blusse(“to blush”), Old Norse blys(“torch”), Danish blus(“blaze”).
Unknown; attested in the late 15th century.
etymonline
blush (v.)
late 14c., bluschen, blischen, "to shine brightly; to look, gaze, stare," probably from Old English blyscan "blush, become red, glow" (glossing Latin rutilare), akin to blyse "torch," from Proto-Germanic *blisk- "to shine, burn," which also yielded words in Low German (Dutch blozen "to blush") and Scandinavian (Danish blusse "to blaze; to blush"); ultimately from PIE *bhel- (1) "to shine, flash, burn."
For vowel evolution, see bury. Sense of "turn red in the face" (from shame, modesty, confusion, etc.) is from c. 1400. Related: Blushed; blushing.
blush (n.)
mid-14c., "a look, a glance" (sense preserved in at first blush "at first glance"), also "a gleam, a gleaming" (late 14c.), from blush (v.). As "a reddening of the face" from 1590s. Meaning "a rosy color" is also from 1590s.
