Rabbit because I had rabbits before chickens. The shadow comes from my black rabbit, Taboo. He is very small, fast, and when he is in the dark, he appears to be just a shadow as he darts around. I often called him the Shadow, or the Shadow Rabbit. Sure, I could have used other names, but his name is the coolest. Oh, and the 10 is only there because I thought you needed a numeral in your username, and 10 is my favorite number.