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]

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Example Sentences

Next to her, a woman named Ksenia shrugged and turned her eye to the sky: "Really, only God knows."

From BBC

“The movie feels very relevant to that theme. God knows, people aren’t always willing to be tolerant.”

From Los Angeles Times

“The Creature learns quickly because its brain and its bodies have already lived once. God knows what this Creature knew before he forgot and needed to be reminded.”

From Los Angeles Times

Joe Shuker, vice president of the America Federal Government Employees Council 100/TSA Region 7, told MSNBC’s Alex Witt on Saturday that workers are having to stretch their last paychecks until “God knows when,” noting that the last government shutdown lasted 35 days.

From Barron's

We walked through tree branches, tangled vines and sharp hanging stalactites, over roots as thick as a human leg, and carcasses of birds, mice and God knows what else in varying states of decay.

From Salon