O.E. flor "floor," from P.Gmc. *floruz "floor" (cf. M.Du. vloer, O.N. flor "floor," M.H.G. vluor, Ger. Flur "field, meadow"), from PIE *plaros (cf. Welsh llawr "ground"), enlarged from *pele- "flat, to spread." The verbal sense of "puzzle, confound" is 1830, from notion of "knock down to the floor" (1640s). Related: Floored; flooring. The figurative sense in legislative assemblies is first recorded 1774. Floor plan attested from 1867.
To shock, surprise, or hurt to the point of helplessness: I was floored when some of our players accepted their offer(1830+)
(also floorboard or floor it) To drive at full speed; push the throttle pedal to the floorboard; put the pedal to the metal: She floored the Porsche on the freeway and got caught/ You better floor it and get out of here(1950s+)