One who strikes or hits; a person who delivers blows or impacts; something that clouts.
From 'clout' (to strike) or 'clour' (to strike) plus '-er' suffix (Old English agent suffix '-ere'). The '-er' suffix transforms verbs into agent nouns naming the person or thing performing the action.
The '-er' suffix is one of English's most productive morphemes—we can add it to almost any verb to create an agent noun ('runner,' 'clouter,' 'tweeter'), which is why English speakers can spontaneously create new occupation and role words that sound perfectly natural to everyone else.
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