1620s, short for plaudite "an actor's request for applause" (1560s), from Latin plaudite! "applaud!" second person plural imperative of plaudere "to clap, strike, beat; applaud, approve," of unknown origin (also in applaud, explode). This was the customary appeal for applause that Roman actors made at the end of a play. In English, the -e went silent then was dropped.
