Late 15th century (in the sense 'blazing, resplendent'): from French, or from Latin flagrant- 'blazing', from the verb flagrare.

• Early senses of flagrant with meanings such as ‘glorious’ and ‘blazing’ were positive. The word comes from the Latin word flagrare ‘to blaze’, as in conflagration (Late Middle English), and is recorded from the late 15th century. Flamboyant (mid 19th century) and flame (Middle English) itself go back to the same root. The Latin original is also found in the phrase in flagrante (delicto) literally ‘in blazing crime’, and usually used to mean that someone has been caught in bed with someone else's partner.