a mocking term for a person with bad eyesight, c. 1500, from blink (v.) + -ard. Figuratively, "one who lacks intellectual perception" (1520s).
Entries linking to blinkard
blink v.
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.
-ard
also -art, from Old French -ard, -art, from German -hard, -hart "hardy," forming the second element in many personal names, often used as an intensifier, but in Middle High German and Dutch used as a pejorative element in common nouns, and thus passing into Middle English in bastard, coward, blaffard ("one who stammers"), etc. It thus became a living element in English, as in buzzard, drunkard. The German element is from Proto-Germanic *-hart/*-hard "bold, hardy" (from PIE root *kar- "hard").