Honour bright

British colloquial expression that means upon my honour used to affirm that what is being said is true dates, according to the OED, from 1819. It is rather old fashioned these days and not frequently heard. People may have unwittingly been quoting Shakespeare because he used the exact phrase in Troilus and Cressida (1603), Act III, Scene III, “Perseverance, my dear lord, keeps honour bright.” It is doubtful, however, that this literal usage by Shakespeare is the origin of the expression as currently used, which the OED maintains is only attested from 1819.