A person or thing that makes a blaring sound; one who blares.
From blare + -er (agent suffix creating 'one who does' the action). This follows standard English word-formation patterns.
Agent suffixes like -er are one of English's most productive tools—you can add -er to almost any verb and create a noun for 'one who does it,' which is why someone with a trumpet is a 'blaoner' and someone with a trombone is a... well, someone with a trombone, because not all words stick around equally.
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