A person or thing that sets something on fire, or archaic usage, something that blazes brightly; one who ignites or causes to blaze.
From the verb 'emblaze' with the suffix '-er' added to create an agent noun—something or someone that performs the action of emblazing.
This word is almost never used today, but it represents an old pattern in English of creating 'do-er' words with '-er'—baker bakes, maker makes, emblazer emblazes. We still use this pattern constantly in modern English without thinking about it.
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