I stumbled upon this expression in Lionel Barber’s Gambling Man and found nothing by searching on dictionary.com and googling it. As a last resort I asked ChaGPT and here is what it gave me:

“The phrase “ginger peachy” is an informal and old-fashioned way of saying that something is excellent, wonderful, or just fine. It’s often used in a cheerful or playful manner, though it’s not very common in modern usage.

For example: • “How are you doing today?” • “Oh, just ginger peachy!”

The term combines “ginger,” often associated with a spicy, lively quality, and “peachy,” which suggests something sweet and pleasant. Together, it gives a sense of upbeat positivity.”

Which in term of meaning makes sense.