Hogwash

google

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mid 15th century: from hog + wash; the original sense was ‘kitchen swill for pigs’.

wiktionary

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From Middle English *hoggewasch (found only as Middle English hoggyswasch(“refuse of the kitchen for feeding pigs”, literally “hog's wash”)), equivalent to hog +‎ wash.

etymonline

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hogwash (n.)

mid-15c., hogges wash, "kitchen slops fed to pigs, refuse of a kitchen or brewery," from hog (n.) + wash (n.). Extended to "cheap liquor" (1712) then to "inferior writing" (1773).