di·min·ish / diˈminish/ • v. make or become less: [tr.] a tax whose purpose is to diminish spending | [intr.] the pain will gradually diminish. ∎  [tr.] make (someone or something) seem less impressive or valuable: the trial has aged and diminished him.PHRASES: (the law of) diminishing returns used to refer to a point at which the level of profits or benefits gained is less than the amount of money or energy invested.DERIVATIVES: di·min·ish·a·ble adj.

diminish XV. Resulting from a conflation of †diminue XIV (- (O)F. diminuer — L. dīminuere) and minish (- OF. menu(i)sier :- Rom. *minūtiāre, f. minūtus MINUTE).
So diminution XIV. — (O)F. — L. diminutive XIV (as sb. in gram.). — (O)F. — late L.