megaphone (n.)

"funnel-like instrument for assisting hearing or magnifying the voice," 1878, coined (perhaps by Thomas Edison, who invented it) from Greek megas "great" (see mega-) + phone "voice" (from PIE root *bha- (2) "to speak, tell, say"). Related: Megaphonic. In Greek, megalophonia meant "grandiloquence," megalophonos "loud-voiced."