In Agatha Christie's And Then There Were None on p. 17, Mr. Blore is listing the characters. He lists the initials CMG and DSO. What do they stand for? The names he lists do total 9.

I'm teaching this book this summer and I know the kids will ask me. I've looked everywhere all over the internet and even at the reference desk in our local library. I even have them highlighted from when I was a kid and had the question about them, but never wrote next to them what they stood for!