for the love of
For the sake of, in consideration of. For example, She signed up for all these volunteer jobs for the love of praise. [c. 1200]
for the love of Pete or Mike or God. An exclamation of surprise, exasperation, or some similar feeling, as in For the love of Pete, give me the money! James Joyce used this idiom in Ulysses (1922): "For the love of Mike listen to him." Pete and Mike are euphemisms for God. [Early 1900s] Also see for the sake of, def. 3.