A person who covets; someone who desires something that belongs to another person.
From 'covet' (Old French 'coveitier') plus the agent suffix '-er' (Old English 'ere'), which creates nouns meaning 'one who does the action.' Originally meant someone consumed with longing.
The '-er' suffix is the most common way to make 'someone who does X'—teacher, singer, builder, runner—and it's been working since Old English times. English speakers instantly understand new ones like 'binge-watcher' or 'cryptocurrency trader'!
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