Heard it through the grapevine
通过传闻或非正式渠道得知消息，并非官方来源。
谈论八卦或未经证实的消息时。
英文释义
You learned something through means of a rumor.
例句
I heard it through the grapevine that they're getting married.
典故来源
源自19世纪美国电报线比喻，葡萄藤状线路传递信息，后指流言传播。