A person who confuses or muddles things; something that causes confusion.
From 'fuddle' plus the agent suffix '-er' (meaning 'one who does'), following the standard English pattern of turning verbs into nouns that name the person performing the action.
The suffix '-er' is one of English's oldest productivity machines—it transforms nearly any verb into a person-noun, which is why we have 'singer,' 'dancer,' 'talker,' and 'fuddler' all following the same blueprint.
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