quid pro quo
Literal translation: something for something
More common meaning: tit for tat
In an English sentence: I hid my friend’s book so, as quid pro quo, she hid my pencil.
Quid pro quo can describe a situation in which one person seeks revenge from another who has harmed him. Here, quid pro quo means “an eye for an eye, a tooth for a tooth.” The phrase can also refer to a situation in which a kind deed is repaid with kindness.
From Elizabeth Heimbach's book Latin Everywhere, Everyday