blink (n.)

1590s, "a glance," of uncertain origin, perhaps from a continental Germanic language; see blink (v.). As is the case with the verb, there is a similar noun in Middle English, from c. 1300, that might represent a native form of the same root. Meaning "action of blinking" is from 1924. From the sense "a flicker, a spark," comes on the blink "nearly extinguished," hence "not functioning" (1901).

blink (v.)

1580s, perhaps from Middle Dutch blinken "to glitter," which is of uncertain origin, possibly, with German blinken "to gleam, sparkle, twinkle," from a nasalized form of base found in Old English blican "to shine, glitter" (from PIE root *bhel- (1) "to shine, flash, burn").

Middle English had blynke (c. 1300) in the sense "a brief gleam or spark," perhaps a variant of blench "to move suddenly or sharply; to raise one's eyelids" (c. 1200), perhaps from the rare Old English blencan "deceive."

Originally with a vague and shifting set of meanings, many now obsolete, having to do with motion of the eyes; in earlier use "the notion of 'glancing' predominates; in the latter, that of 'winking'" [OED]. Meaning "cast a sudden, fleeting light" is from 1786; that of "shut the eyes momentarily and involuntarily" is from 1858. Related: Blinked; blinking. The last, as a euphemism for a stronger word, is attested by 1914.