The pager was a type of communciations device used on Earth in the late 20th century. This device would alert its user to a recently received message by beeping. These devices were used by people who needed to be contacted quickly, such as doctors. Due to where they were usually stored on a person, some people nicknamed these devices "pocket pagers".
In 1986, while being at a Italian restaurant for dinner, James T. Kirk's communicator beeped several times. His dining companion, Doctor Gillian Taylor, asked him if he had one of these devices and if he was a doctor. (Star Trek IV: The Voyage Home)