My 12 year old deserves credit for this question.

He asked "Why do we say 'by accident' but not 'by purpose' "

I was stumped - this is an embarrassing situation! Searching left me cold. The nearest result I could find was Is it correct to say "on accident" instead of "by accident"? but this is a different question.

We also say "by chance" rather than "on chance".

So, can anyone help me be Dad-who-knows-all again?


1 Answer 1


I think it is a question of idiomatic usage, on purpose is an idiomatic expression which dates back to the latter part of the 16th century:.

  • "by design" is attested from 1580s.

Its earlier foorm was "of purpose (early 15c.)" probably from the French "de propos".


Note also the expression : accidentally on purpose:


  • The first printed record of this phrase that I can find is from The history of the famous preacher Friar Gerund de Campazas, by José Francisco de Isla, 1772:

    • Tell us what is Modesty of Voice, for you happened accidentally on purpose to drop this word, and I don't rightly know what it signifies.

The Phrase Finder

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