Quid pro quo is a Latin phrase and is most similar to the phrases ‘give and take’ and ‘tit for tat’. Initially, in the 1500s, the phrase implied substitution such as the substitution of one medicine for the other (the phrase has originally been used in late medieval pharmaceutical compilations). By the late 1600s, the meaning of the phrase extended itself to personal gain or reciprocity. Today the phrase lends itself to legalese and business exchanges. In his book Think and Grow Rich, Andrew Carnegie has explained that quid pro quo is the law of the marketplace.
The phrase also has its negative connotations. In legalese, quid pro quo is used in reference to sexual harassment when favors are requested in return for a promotion, etc.
Here are some instances of the use of the phrase in literature:
“A pun on the Latin expression quid pro quo, meaning an equal exchange (this for that), and the British word quid, meaning a pound sterling.”
— Ambrose Bierce, The Unabridged Devil’s Dictionary
“To use our individual good or bad luck as a litmus test to determine whether or not God exists constructs an illogical dichotomy that reduces our capacity for true compassion. It implies a pious quid pro quo that defies history, reality, ethics, and reason. It fails to acknowledge that the other half of rising–the very half that makes rising necessary–is having first been nailed to the cross.”
― Tiny Beautiful Things: Advice on Love and Life from Dear Sugar