grapevine 是葡萄藤，through the grapevine通过葡萄藤，表达的意思却是“小道消息；道听途说”。

【例句】
Don't believe anything through the grapevine. There are more and more gossipers.
不要听任何小道消息，此刻传闲话的人越来越多了。

It's not announced officially yet, but this morning I got it through the grapevine.
这个消息还没有正式宣布，我是今天早上通过小道消息听来的。