Green’s Dictionary of Slang

a euph. for God; in phr. such as golly for you or golly help you.

1917		‘Henry Handel Richardson’ Aus. Felix (1971) 17: His plucky exploit [...] blazed its way through the settlement; and blarney and bravos rained upon him. ‘Golly for you, Purdy, old ’oss!’.
1919		F. Hurst Humoresque 6: I’m goin’, ma; for golly sakes, I’m goin’!
1946		R.L. Bellem ‘Latin Blood’ in Speed Detective Aug. 🌐 But golly help you if you’re needling me.
1969		P. Theroux Murder in Mount Holly (1999) 63: ‘For golly sake!’ she said.