cui bono en · NOUN
Etymology
From Cicero’s Pro Sexto Roscio Amerino, 84 & 86: Latin cui bonō fuisset (“to whom it would have benefited”), a so-called double dative construction.
Meanings
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(uncountable) The principle that the ultimate initiator of an action is likely the person who stands to gain from the action.
If the principle of cui bono is applied, it is evident that the gainers were the party of the triumvirs, whose popularity would be increased by a belief being created that their opponents the Optimates were prepared to adopt extreme measures to get rid of them.
1900, Evelyn Shuckburgh, Letters to Atticus, translation of original by Marcus Tullius Cicero: