Idiot Proof

[WhatCFeryIsThis]

Recently I've noticed my father in law has always said 'idiot proof' to mean that an idiot is unable to use a specific object that he's struggling with. I can see his logic, but I've always thought that 'idiot proof' meant that 'even the most idiotic of idiots can use this simple thing'.

Opinions please!

You are right.

You are right. But I get what he means!

Yet child safe means a child shouldn't be able to open it in the case of medicines for example.

You need the hyphen. Idiot-proof.
You're right, but I think his interpretation is technically correct. If x is y-proof, it generally means y is prevented from using it/ getting in etc. Had never thought of that before! I can't think of many times I'd need to describe something like that though.

Ah, I forgot the hyphen. And yes, anything else that's 'x-proof' tends to be unusable by 'x'. I wonder why 'idiot-proof' has almost the opposite meaning? 🤔

But doesn't "idiot-proof" mean designed so an idiot can't use it incorrectly? If the solution to that is stop the idiot from using it at all, then that fulfils the objective of idiot-proof.

So, child-proof means it blocks the child because for a child to use it would be incorrect. If an item is water-proof, it's not that it can't get wet, it just stops the water from reaching the wrong place.

In any case, isn't OP's FIL just using some self-deprecating humour about being an idiot?

@DadDadDad definitely self-deprecating, but I am in no doubt that he believes it means 'can't be used by idiots'. I still find it endearing though! And like PPs I was surprised that I had never really considered this phrase before FIL came along with his interpretation.

@WhatCFeryIsThis - I think there's a phrase that originated in IT, that they keep trying to make computers idiot-proof, but the universe keeps providing bigger idiots! Maybe your FIL could offer his services as an "idiot" to test new products.