come out of the woodwork

Reader's Digest 5月号の記事 Perfect Strangersから引用します。
So she launched a Facebook Group called Make Lincoln Kind Again. Members have made cards for seniors, assembled hygiene bags for womem in need, and gathered supplies for an incoming refugee family. There's some karma at play, too: When Nightenale had a stroke in January, members rallied to make hospital visits and look after her kids. "It's amazing to see people you barely know come out of the woodwork to support you," she says.
慣用句らしい "come out of the woodwork" の意味を調べます。
・Wiktionary: to appear or emerge unexpectedly or inexplicably, frequently in large numbers or quantity.: He won the lottery last year and he has had old "friends" and distant relatives coming out of the woodwork ever since.
Etymology: From the idea of insects crawling out from inside the woodwork in a house
・Farlex Dictionary of Idioms: To appear unexpectedly, or from unexpected places.: Ever since Liam won the lottery, his so-called relatives have been coming out of the woodwork.
似た表現の "crawl out of the woodwork" を 12/24/2013 に取り上げていました。