c. 1300, "one who speaks," agent noun from speak (v.). Similar formation in Old Frisian spreker, Old High German sprahhari, German Sprecher. First applied to "person who presides over an assembly" c. 1400, from similar use in Anglo-French (late 14c.) in reference to the English Parliament; later extended to the U.S. House of Representatives, etc. The electric amplifier so called from 1926, short for loud-speaker.
