God knows

• God only knows, goodness knows, gosh knows
• heaven knows, heaven only knows
• Lord knows, Lord only knows

God knows

1. It is only known to God; it is unknown to people.

   Synonyms: I don't know, who knows

   Don't touch that! God knows who else put their hands on that thing!

   • 1837, Moses Stuart, A Commentary on the Epistle to the Hebrews, 4th edition, page 73:

     […] Origen himself does not say this. His words are simply, "Who wrote it [i.e. penned it down], God knows, ἡ δὲ εἰς ἡμᾶς φθάσασα ἱστορία", but a report has come to us, that it was either Clement or Luke.

   • 1994, Daryl Simmons & Babyface (lyrics and music), “Willing to Forgive”, performed by Aretha Franklin:

     I paid the rent, washed your clothes / Cooked your food and only God knows / Only God knows why I stay with you / I guess I'm in love

   • 1995, Tom Gammill and Max Pross, “The Gum”, in Seinfeld, season 7, episode 10 (television production):

     So, you want my father to pay for this? – You saw him. He was fiddling with the engine. God knows what he did there.

2. (often modifying a parenthetic concession) It is known unto God; it is certainly true.

   Synonyms: certainly, of course, obviously

   God knows many kids don't like going to school!

   • 1700 August 8, Matthew Henry, “A Sermon Preached at the Opening of the New Meeting-House at Chester”, in Misc. Works, published 1830, page 1134:

     […] those therefore that appeal to him^[sic] upon every trivial occasion, and with a slightly superficial God knows, while they never think of God, nor have any regard to his^[sic] knowledge, profane his^[sic] name by taking it in vain […]

   • 1984, Joseph Heller, God Knows, page 8:

     I have my faults, God knows, and I may even be among the first to admit them, but to this very day I know in my bones that I'm a much better person than He is.

   • 1992, Larry David, “The Contest”, in Seinfeld, season 4, episode 11 (television production):

     No, no, no. Don't do it. Don't do it! For my sake! God knows I don't ask you for much! Now, come on. Please, Jerry. Please! I'm beggin' ya! Please! Come on! Please!

In the sense “nobody knows”, an interrogative pronoun often follows: “God knows where”, “God knows why” etc.

• God knew