A minced oath of "God knows."
1. No one knows. (A variant of "God knows.") Gosh knows how long it will take for my application to be processed. A: "How do you think you did on your exam?" B: "Gosh knows!"
2. It is absolutely true, certain, or definite (that something is true or the case). Gosh knows I need to do well on this test, or I can kiss my scholarship goodbye!
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.