When we hear telegraph, we often think of the device developed and patented in 1837 by Samuel Morse for sending messages across long distances by way of electromagnetic signals. However, the word telegraph did not originate with the electric telegraph; that word can refer to any kind of process of communicating at a distance other than using speech, such as semaphore.
The telegraph device has long been supplanted by telephones and electronic communication, but telegraph survives in English as a verb meaning “to communicate or make known by signs especially unknowingly.”
In between are rows of booths with bench seating, telegraphing this is a come-and-go restaurant built for quick slurping.
— Sue Kidd, The News Tribune (Tacoma, Wash.), 9 May 2018
Boxers are said to be at a disadvantage when they telegraph punches, using body movements unconsciously to indicate to the opponent what kind of punch is about to be thrown.