The phrase “going postal,” which means to become uncontrollably angry, appeared as a slang term in American English in the 1990s. It emerged after a spate of shootings at post offices carried out by employees who were angry about their working conditions.
The first recorded use of the term came in 1993, when a Florida newspaper printed an article about the post office murders. By that time, at least 11 such tragedies had occurred — but there were more to come.
These shootings became so commonplace that the United States Postal Service even created a new position, the Workplace Environment Analyst. The workers hired to fill these jobs were tasked with preventing violence and improving workplace conditions, though this was no easy task.