A person or device that catches beetles, or someone who studies beetles; also a tool used in printing or papermaking.
From 'beetle' plus the agent suffix '-er' (from Old English), meaning 'one who beetles' or 'a device that beetles,' following the standard English pattern for creating agent nouns.
A 'beetler' in printing is a heavy metal hammer that compacts paper—the repetitive pounding motion matched the scurrying movement of beetles so well that printers named the tool after them.
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