Word Origin & History
1580s, "member of an ancient Gk. school that doubted the possibility of real knowledge," from Fr. sceptique, from L. scepticus, from Gk. skeptikos (pl. Skeptikoi "the Skeptics"), lit. "inquiring, reflective," the name taken by the disciples of the Gk. philosopher Pyrrho (c.360-c.270 B.C.E.), from skeptesthai
"to reflect, look, view" (see scope
(1)). The extended sense of "one with a doubting attitude" first recorded 1610s. The sk- spelling is an early 17c. Gk. revival and is preferred in U.S.
"Skeptic does not mean him who doubts, but him who investigates or researches as opposed to him who asserts and thinks that he has found." [Miguel de Unamuno, "Essays and Soliloquies," 1924]