blinker (n.)

1630s, "one who blinks," agent noun from blink (v.). As a type of horse eye screen to keep the animal looking straight ahead, from 1789 (compare blinder). Slang meaning "the eye" is from 1816. Meaning "intermittent flashing light" is from 1923.

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Definitions of blinker from WordNet
blinker (n.)
a light that flashes on and off; used as a signal or to send messages;
Synonyms: flasher
blinker (n.)
a blinking light on a motor vehicle that indicates the direction in which the vehicle is about to turn;
Synonyms: turn signal / turn indicator / trafficator
blinker (n.)
blind consisting of a leather eyepatch sewn to the side of the halter that prevents a horse from seeing something on either side;
Synonyms: winker / blinder
blinker (v.)
put blinders on (a horse);