According to Gavin White, the Mag Dog constellation (MUL UR IDIM) is an Akkadian name borrowed from the Sumerian. UR being large beast; lions wolves dogs. And is associated with the Uridimmu a rare figure first seen in Kassite art having a human head and torso on lion's hindquarters. A late invention often paired with Bison-man that appears next to Scorpio.Quote
As I stated much earlier, in Mesopotamia (where the zodiac comes from - Egypt didn't have one,) the constellation was originally referred to as the "Big Dog."
He also writes that there were 4 original constellations, one being the Great Lion or Dog which later spilt into the Furrow (becoming a goddess with wheat and corn), and the Weighing Scales