Today's OED antedating: "(oh) boy!"

(Oh) boy!, colloquial, jocular, essentially meaningless albeit exuberantly jubilant exclamation ("boy," n.1, sec 9, first use cited 1917): Poem titled "'Persicos Odi,'" by Franklin P. Adams, collected in Weights and Measures, 1917, p 84: "Oh, boy!—to quote a slangy line—/This war-stock thing is wrong."