Plural of chump; people who are easily fooled or tricked, or who are stupid and gullible.
From 'chump,' which likely comes from a combination of 'chunk' and 'lump,' first appearing in print in the 1880s. The idea is that a chump is a thick, stupid person, like a block of wood.
The word 'chump' probably started as a visual joke—you call someone thick, dumb, or block-headed when they're foolish, so 'chunk-like' became slang for a fool, and it stuck.
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