Definition of "good night"

[…] peculiarities of your law always interest me. What is 'legitim'?""Oh! Good-night!" I said derisively."But I am in dead earnest, and really want to know," he added with a perfectly serious face; "I have a small bet on."

1920, William Darling Lyell, The House in Queen Anne Square: A Tale, page 34

Together they pried into the sodden mass, yanking out what was left of the record books."Oh, good night!" Joe moaned in dismay. "The fire extinguisher liquid has messed up what the fire didn't."

1954, Franklin W. Dixon, The Yellow Feather Mystery