The phrase quid pro quo means "what for what" in Latin, but that makes very little sense to me. Wikipedia hints at the original meaning having to do with substitutions. That makes sense, as pro can indeed be used when substituting something for something.

But how was the Latin phrase originally used within Latin? Was it part of a longer phrase? Was pro quo (a part of) a relative clause or a question? When did it appear? Or was the phrase ever in any real use in Latin? Any light on the Latin usage that was borrowed into other languages would be helpful. (Although I do assume that the meaning in Latin was different from what it means in English today.) In particular, examples of use in a Latin sentence would be great.

The phrase pro quo is, unsurprisingly, very frequent in classical Latin. But I found no quid pro quo in this corpus.

  • Possibly quid is late from quisquis; and quo is relative, meaning (Eng slang) 'whatever.'
    – Hugh
    Nov 21, 2019 at 18:07
  • @Hugh What's wrong with quid as nominative neuter singular of quis?
    – luchonacho
    Nov 21, 2019 at 18:50
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    Er, ...... what?
    – Hugh
    Nov 21, 2019 at 20:14
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    L&S give examples of quis =anyone, someone; but no quotations for quid =anything, something, except with specific conjunctions. Quiquid, quidlibet, ne quid, are given. May just be an accident of compilation.
    – Hugh
    Nov 22, 2019 at 3:35
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    @Hugh I'm used to seeing both quis & quid as "some" with particles like ne or si but not alone. Therefore the reading "something for something" throws me off, but it could indeed be idiomatic not to use aliquid or similar in later Latin.
    – Joonas Ilmavirta
    Nov 22, 2019 at 6:35

2 Answers 2


There is a superb (and very long) answer to a related question here. I won't reproduce it here, but some quotes from the post:

(question) I am not a native English speaker; I am Italian. I am always puzzled when I hear the expression "quid pro quo" intended as "you scratch my back I scratch yours". In Italy we mean it as "misunderstanding" (from the literal translation "this for that", with "for" meaning "in the place of" rather than "in exchange for").

(answer) The phrase "quid pro quo" has appeared in texts written otherwise mostly in English for at least 490 years. The earliest example I found was from 1528, but I would not be at all surprised if even older examples exist.

The earliest examples of "quid pro quo" in English come arise in two distinct contexts: law (no later than 1528) and medicine (no later than 1535). And critically, the sense of the phrase "something for something" differs in the two fields.

To my mind, the likeliest explanation for the divergence between Italian "quid pro quo" as misunderstanding and English "quid pro quo" as mutually advantageous arrangement is that Italian, like French, embraced the term through its medical/apothecary tradition whereas English ultimately abandoned that tradition of use in favor of the English common law sense of the term.

And another answer:

The English phase is derived from European medieval latin, primarily from religious, philosophical, legal and classical rhetorical texts.

Italian, in contrast, developed organically directly from latin through daily use in everyday conversation so there was an opportunity for the meaning to drift from the formal written textual usage, into one that comes up in everyday life but not in the kind of formal texts that provided a basis for the borrowing of the phrase into English. So, the meanings of the phrase diverged from the common original vernacular Latin origin on two different trajectories.

All in all, it seems the phrase does not appear originally in Latin texts. According to "The Concise Oxford Dictionary of English Etymology":

(in apothecaries' language) one thing in place of another; one thing in return for another, tit for tat. XVI. — L. quid something, prō for, instead of, quō (abl. of quid) something.

From the above, I don't understand exactly why the phrase does not "make sense". Although quis does mean "what", it can also mean "something", as the entry above states. L&S concurs, giving several examples from Classical Latin. So, although the phrase might not be used in a classical Latin content, I venture it would have made perfect sense to a Roman.

  • Thanks! The question was specifically about the use of that phrase in Latin, not in other languages. I took quid to mean "what" (interrogative or relative), and the meaning "what for what" was hard to imagine in use. While it is legitimate, I find it weird to use quid for "something" in such a phrase. // Do you happen to have any use examples of the phrase in Latin?
    – Joonas Ilmavirta
    Nov 21, 2019 at 20:03
  • Curious if anyone uses quid pro aliquo for the French (medical) meaning.
    – C Monsour
    Nov 21, 2019 at 22:37

According to Lexico it's origin as a phrase is mid-16th century medicine, and correlates with Wikipedia hinting that it's substituting one thing for another.

Merriam-Webster gives a little bit more insight as well. It also gives the first known use as 1582, but doesn't provide a source for what that is.

My guess from that is there is probably no classical usage of it like that, and the 16th century origin could explain why it's a somewhat strange phrase.

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    For a full sentence description of roughly what we call quid pro quo, the ancient Romans would say manus manum lavat.
    – C Monsour
    Nov 21, 2019 at 1:09
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    @CMonsour: However that can have a negative meaning, like mutual omerta: "close an eye on this, and I'll do you a favour later" - indeed,the corresponding una mano lava l'altra in Italian has this only meaning. Instead do ut des was used in Latin and still is used in Romance languages to indicate what quid pro quo is used for in English - quoting Wikipedia in the following- while quid pro quo (or qui pro quo, as widely used in Italian, French and Spanish) retains its original meaning of something being unwillingly mistaken,or erroneously told or understood, instead of something else. Nov 21, 2019 at 7:30
  • @VicenzoOliva I agree with you about what all of these phrases mean in Latin. However, quid pro quo tends to have a negative meaning in English. Perhaps not as negative as manus manum lavat, but closer to that than to do ut des. One would use do ut des to describe a religious sacrifice, for example, but English quid pro quo would feel inappropriate for that.
    – C Monsour
    Nov 21, 2019 at 22:18
  • @CMonsour: In fact, the example of a religious sacrifice is great to show what I was saying: the Romans described it as do ut des, while one can find plenty of English sources using quid pro quo to describe it. Nov 21, 2019 at 22:53
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    @VincenzoOliva Interesting. I usually find do ut des for religious sacrifice even in English, unless the attitude of the author is hostile.
    – C Monsour
    Nov 21, 2019 at 22:59

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