Plural of blighter; something or someone that causes blight, or British slang for annoying people or things.
From 'blight' (disease, ruin) plus '-er' agent suffix, creating a noun for things causing damage; heavily used in British slang as mild insult since 19th century.
British soldiers in WWI coined 'blighters' as affectionate insult for enemies and comrades alike—a word that started technical (plant disease) became a cultural personality marker.
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