1677, "a trick, a hoax, a fraud," perhaps from sham,
a northern dialectal variant of shame
(q.v.). Sense of "Something meant to be mistaken for something else" is from 1728. The meaning in pillow-sham
(1721) is from the notion of "counterfeit." The adj. is attested from 1681; the verb from 1677. Shamateur
"amateur sportsman who acts like a professional" is from 1896.