Overflow

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Old English oferflōwan (see over-, flow).

wiktionary

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From Middle English overflowen, from Old English oferflōwan, equivalent to over- +‎ flow.

etymonline

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overflow (v.)

Middle English overflouen, from Old English oferfleow "to flow across, flood, inundate," also "to flow over (a brim or bank);" see over- + flow (v.). Common Germanic (Old High German ubarfliozan, German überfliessen, etc.). Related: Overflowed; overflowing.

overflow (n.)

1580s, "act of overflowing, an inundation," also "the excess that flows over," from overflow (v.).