 Perhaps for the same reason, "foolproof" is now a formal term, whereas "idiot-proof" remains informal.Both terms are originally adjectives ("a foolproof plan"), but can be used as verbs ("foolproof this design").Several Murphy's law adages claim that idiot-proof systems cannot be made, for example "Nothing is foolproof to a sufficiently talented fool" and "If you make something idiot-proof, someone will just make a better idiot."