A Nod Is As Good As a Wink... to a Blind Horse was created in 1971-03.

It's not an idiom, it's a saying. If the horse is blind, it can't see either the nod or the wink, so they'd mean the same thing to the horse. You nod when you're agreeing and you wink when you're sneaking around with something.

A nod is as good as a wink to a blind horse.

i think this is an amalgamation of 'a winks as good as a nod to a blind man', and, a word is enough to the wise (and a few other variations). hope this helps.

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