I BELIEVE YOU, phr. (common).—A general assent; ‘yes’: sometimes, ‘I BELIEVE YOU MY BOY.’ [Once a favourite catch-phrase of a well-known actor].

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  1835.  DICKENS, Sketches by Boz, 286. ‘Now confess: were you not a little surprised?’—‘I BELIEVE YOU,’ replied that illustrious person.

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  1849–50.  THACKERAY, Pendennis, I., 140. ‘Miss Rouney, I gather, was the confidante of the other.’ ‘Confidante? I BELIEVE YOU.’

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  1860.  G. ELIOT, The Mill on the Floss, 199. ‘Is she a cross woman?’—‘I BELIEVE YOU.’

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  1870.  DUDLEY COSTELLO, The Millionaire of Mincing Lane, 204. ‘And she hates that fellow?’—‘Hates him? I BELIEVE YOU.’

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