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.

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