God knows

Idioms  

1. Also, goodness knows; heaven knows.

2. Truly, certainly, definitely, as in God knows I need a winter coat . This expression, which originated about 1300 as God wot , does not necessarily imply that God is all-knowing but merely emphasizes the truth of the statement it accompanies. The variants using goodness and heaven are euphemisms that avoid taking God's name in vain. [Second half of 1500s]

3. Also, God only knows . Only God knows, that is, neither I nor anyone else knows, as in God knows where I've stored those photos , or God only knows how many people will join the march . [Second half of 1500s]

---

Example Sentences

"I'm from a low income background so I have maximum student finance, so what that means for the future, god knows how much I'll be paying," she added.

From BBC

"It's ruined my life - we're going to be in debt for God knows how long paying it off," she says.

From BBC

This man wouldn’t even let kids he’d thrown together from God knows where get to know each other, much less hire a pair of friends!

From Literature

“Aye. It seems—and only God knows how, because it should be impossible —that the glimourie is fading. And it’s the glimourie that all magical creatures depend on. It’s in everything—in the air, in the water, in the earth. But the creatures are suffocating in the ocean. There’ve been stories of longmas eating each other.”

From Literature

I have a strong mind, and I believe God knows their hearts.

From BBC