This idiom means getting information from an informal source by word of mouth; usually via gossip or rumor mill.
Where did it come from?
The term “heard it through the grapevine” is really an allusion. Its “roots” began in 1844 when Samuel Morse gave the first public demonstration of the telegraph, sending a message from Baltimore to Washington. It was heralded as the most rapid way of transmitting information from one place to another.
There are two possibilities for the coining of the term. The first is that rapid information transfer of the telegraph lead to the realization that close communities already had such a device in the spreading of news and gossip via word of mouth. Most of these communities were tight-knit rural people. Hence, it was likened to the fast growing and intrusive tendrils of a grapevine.
It’s also been said the term was birthed during the Civil War because the telegraph wires were likened, metaphorically, to grapevines.
By 1852, “heard it through the grapevine” made its way into print in the first U.S. dictionary.
Not all grapevine-style communication is bad. According to Wikipedia, Jitendra Mishra derived 8 reasons Grapevine communication Exists. Some of the reasons include the need for faster communication, useful messages transmitted, outlets for imagination and apprehension, and helps build teamwork and corporate identity. Surprisingly, 75% of all organizations’ practices, policies, and procedures are shared through grapevine communication. Though there is a negative thought about grapevine communication , studies have shown the employees find informal communication such as grapevine communication to be more effective than formal channels of communication because it coexists with the formal communication system.
In 1901, in Booker T. Washington‘s Up from Slavery, he refers to the “grapevine telegraph” as:
Often the slaves got knowledge of the results of great battles before the white people received it. This news was usually gotten from the coloured man who was sent to the post office for the mail… The man who was sent to the post office would linger about the place long enough to get the drift of the conversation from the group of white people who naturally congregated there, after receiving their mail, to discuss the latest news. The mail carrier on his way back to our master’s house would as naturally retell the news that he had secured among the slaves, and in this way they often heard of important events before the white people at the ‘big house,’ as the master’s house was called.
Either way, this method for sharing information is an indelible and important part of society.