تعریف و معنای "[hear] {sth} (through|on) the grapevine"

What is the origin of the idiom "hear something through the grapevine" and when to use it?

The idiom "hear something through the grapevine" has its roots in the image of information spreading like wildfire through a network of interconnected grapevines or vines. It was popularized in the 19th century, and its precise origin is somewhat unclear. This idiomatic expression is used when someone learns about a piece of information or gossip indirectly, often through unofficial or informal channels rather than through direct communication. It implies that the information has been passed from person to person, similar to how news might spread through a network of grapevines. It is commonly used in informal conversations.