metronome (n.) Look up metronome at Dictionary.com
mechanical musical time-keeper, 1815, coined in English from Greek metron "measure" (see meter (n.2)) + -nomos "regulating," verbal adjective of nemein "to regulate," from PIE root *nem- "to divide, distribute, allot" (see nemesis). The device invented 1815 by Johann Maelzel (1772-1838), German civil engineer and showman. Related: Metronomic.