turn a blind eye
idiom

- to pretend you do not notice something, because you should do something about it but you do not want to

MacMillan Dictionary

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ORIGIN

The phrase to turn a blind eye is attributed to an incident in the life of Admiral Horatio Nelson. Nelson was blinded in one eye early in his Royal Navy career.

During the Battle of Copenhagen in 1801 the cautious Admiral Sir Hyde Parker, in overall command of the British forces, sent a signal to Nelson's forces ordering them to discontinue the action.

Naval orders were transmitted via a system of signal flags at that time. When this order was brought to the more aggressive Nelson's attention, he lifted his telescope up to his blind eye, saying:

"I have a right to be blind sometimes. I really do not see the signal," and most of his forces continued to press home a successful attack.

Later that day Nelson openly stated that he had "fought contrary to orders". Sir Hyde Parker was recalled in disgrace and Nelson appointed Commander-in-Chief of the fleet following the battle.*

The Oxford English Dictionary records usage of the phrase as early as 1698

* Pope, Dudley (1972) "The Great Gamble: Nelson at Copenhagen"

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SYNONYMS

overlook, disregard, neglect, ignore, pay no attention/heed to, pass over, omit, skip, gloss over, leave out, leave undone, look the other way, wink at, sweep aside

noun = willful blindness

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Practice OWAD in a conversation today, say something like:

"We’re not supposed to park here, but the authorities usually TURN A BLIND EYE."