Foolproof means so simple that nobody could get it wrong. A foolproof method, foolproof instructions, nothing is foolproof.
It is a claim reality tends to test, and the engineer's answer is that fools are ingenious. A genuinely foolproof design makes the wrong action physically impossible rather than merely discouraged, which is how safety engineering actually works.
1adjectivefoolproofSo simple that nobody could get it wrong.
“The instructions were so clear that the recipe was completely foolproof.”
foolproof is a quality.
Middle English
fol
English
fool
English, today
foolproof
From fool + -proof. fool comes from Middle English fol. From Middle English fol (“fool”), from Old French fol (cf. modern French fou (“mad”)) from Latin follis. a doublet of fals and follis. Displaced native Old English dwæs.
Etymology from Wiktionary, CC BY-SA