"Golly!"

GEE

Think of what a surprised cowboy might exclaim when urging a horse forward—it’s also a mild oath.

"Golly!" is an old-fashioned exclamation of surprise, often used in a lighthearted or innocent way. The answer "GEE" works because it’s a shortened, informal version of the same kind of exclamation—like saying "Gee whiz!" Both words express mild astonishment, making them close in meaning and tone. The clue plays on the idea that "Golly" and "Gee" are essentially the same kind of interjection, just with slightly different phrasing.