725: quid pro quo Dec 2, 2016

In addition to many adopted words from Latin, English has acquired some entire phrases, including 'pro bono', 'status quo', 'a priori', and 'quid pro quo', just to name a few. These all have literal meanings, but that doesn't prevent a phrase from being used in different ways. 'Quid pro quo' which in English is, 'something for something' first denoted an item one got from an apothecary, referring to the process of replacing one medicine for another, intentional or otherwise. A few decades later the meaning was extended to other exchanges, and now the initial sense from its early years of being an English term is rarely if ever the intended meaning.