blinker (n.)

1580s, "nictitate, wink rapidly and repeatedly," perhaps from Middle Dutch blinken "to glitter," which is of uncertain origin, possibly, along 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."

The word existed 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].

Blink as "to wink" is attested by 1761. The 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 adjective, is attested by 1914.

"one who or that which blinds," 1580s, agent noun from blind (v.). In 19c. use, especially of blinkers for horses (1809), and often figurative. They were said to prevent the horse being startled by peripheral movements and to keep it steady at its work, but many equestrian authorities railed against them as cruel and unnecessary. Related: Blinders.

in the figurative sense, 1849, from horses being fitted with blinders to limit the range of their vision (see blinker).