1590s, "pertaining to Pyrrho" (Greek Pyrrhōn, c. 360-c. 275 B.C.E.), skeptic philosopher of Elis, who held the impossibility of attaining certainty of knowledge. The name means "reddish" or "red-haired," from pyrrhos "flame-colored," from pyr "fire" (from PIE root *paewr- "fire"). Related: Pyrrhonism; Pyrrhonist.
The doctrine of Pyrrho was that there is just as much to be said for as against any opinion whatever ; that neither the senses nor the reason are to be trusted in the least ; and that when we are once convinced we can know nothing, we cease to care, and in this way alone can attain happiness. It is said that Pyrrho would take no ordinary practical precautions, such as getting out of the way of vehicles. [Century Dictionary]