early 15c., "to furnish with a floor," from floor (n.). Sense of "puzzle, confound" is from 1830, a figurative use, from earlier sense of "knock down to the floor" (1640s). Colloquial floor it "press down hard on the accelerator pedal of a motor vehicle" is by 1986 (compare earlier step on it in the same sense). In mid-19c. English university slang, it meant "do thoroughly and successfully" (1852). Related: Floored; flooring.
<a href="https://www.etymonline.com/word/flooring">Etymology of flooring by etymonline</a>
Harper, D. (n.d.). Etymology of flooring. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/flooring