Chump

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early 18th century (in the sense ‘thick lump of wood’): probably a blend of chunk1 and lump1 or stump.

wiktionary

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Origin unknown. Perhaps a nasalised variant of chub(“someone chubby, something thick”). Compare Icelandic kumbr(“a chopping”), English chop. Probably related to chunk.

Variant of chomp, itself a variant of champ(“to bite”). More at champ.

etymonline

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chump (n.)

1703, "short, thick lump of wood," of uncertain origin, perhaps a variant of chunk (n.) or a nasalized variant of chub (compare chuck/chunk and Old Norse kumbr for kubbr "block of wood"). Meaning "blockhead" is first attested 1883. Chump change attested by 1950.