buzzer (n.)

late 15c. (buzzing is from late 14c.), echoic of bees and other insects. The aviation sense of "fly low and close" is by 1941 (see buzz (n.)). Related: Buzzed. To buzz off "go away quickly" (1914) originally meant "to ring off on the telephone," from the use of buzzers to signal a call or message on old systems. As a command, it originally would have been telling someone to get off the line.