1560s, back-formation from exclamation or else from Middle French exclamer (16c.), from Latin exclamare "cry out loud, call out," from ex- "out," or else here as an intensive prefix (see ex-) + clamare "cry, shout, call" (see claim (v.)). Spelling influenced by claim. Related: Exclaimed; exclaiming.[exclaim etymology, exclaim origin, 英语词源]