howler (n.)

1800, "animal that howls," originally in reference to the South American monkey, agent noun from howl (v.). Meaning "glaring blunder, ridiculous mistake" is first recorded 1890. In early telephony (1886 - c. 1920) the name of a device used by the exchange to produce a loud howl in the receiver to attract a subscriber who has not hung up his end of the connection.

Telephone companies are oftentimes annoyed by subscribers leaving the receivers off the hook—time is lost and the service is more or less impaired. The Kellogg Switchboard & Supply Company has recently issued a four-page folder descriptive of their "howler" equipment which is effectively used in remedying this evil. [Journal of Electricity, Power & Gas, vol. xxix, no. 6, Aug. 10, 1912]