Something or someone that hits with heavy, loud blows, or a large object that makes a thumping sound.
From 'thump' (a heavy blow), which comes from onomatopoeia (imitating the sound). The suffix '-er' makes it an agent noun meaning 'one who thumps.'
Rabbits thump their back legs on the ground as a warning signal to other rabbits—so a rabbit can be called a 'thumper'—and this earned them a reputation as thumpers in folklore before Bambi!
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