1570s, of accounts, "to reduce to order, to set out clearly" (a sense now obsolete), from Late Latin or Medieval Latin liquidatus, past participle of liquidare "to melt, make liquid, make clear, clarify," from Latin liquidus "fluid, liquid, moist" (see liquid (adj.)). Sense of "clear away" (a debt) first recorded 1755. The meaning "wipe out, kill" is from 1924, possibly from Russian likvidirovat, ultimately from the Latin word. Related: Liquidated; liquidating.
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Harper, D. (n.d.). Etymology of liquidator. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/liquidator