'emblazon' originates from the combination of the prefix 'em-' (a variant of 'en-', meaning 'to cause to be' or 'put into') and the verb 'blazon' (from Old French 'blason', meaning 'shield' or 'heraldic device').

'blazon' came into English from Old French 'blason' referring to a shield or coat of arms; in Middle English the prefix 'em-' was attached to form 'emblasonen' (or similar spellings), which later became the modern English 'emblazon'.

Initially it referred specifically to depicting or painting a coat of arms or heraldic device; over time it broadened to mean decorating or displaying prominently and, by extension, proclaiming or publicizing widely.