We know that the idiom TO TURN A BLIND EYE means to pretend not to notice something but where did this term originate from?
In the naval battle of Copenhagen (1801) Admiral Sir Hyde Parker leading the British fleet, sent a flag signal to his second in command Admiral Horatio Nelson (who was blinded in one eye in an earlier naval battle) to withdraw against the Danish/Norwegian army.
The one-eyed Nelson was convinced they could win the battle so he deliberately ignored his superiors’ signal by putting his telescope to his blind-eye thus pretending not to ‘see’ the waving flag signalling them to retreat.
Fortunately the British won the battle thanks to Nelson ‘turning a blind eye’ & making a decision to go ahead with his troops to attack.
(An IDIOM is a word, phrase or an expression that has a different figurative meaning than its literal meaning)