Plural of heller; a person who raises hell or causes trouble; in historical contexts, a large medieval coin or a person who worked in helleries (mining).
From Hell plus -er (one who does). In medieval German, a heller was a silver coin minted in the city of Hall; later it came to mean a troublemaker in English slang.
Hellers, the medieval coins, were so common that they became synonymous with small change—like how we say 'not worth a penny.' But calling someone a 'heller' meant they caused mischief, which is why the word eventually meant a troublemaker rather than currency.
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