Literally, a log of dog poop. Used as a pejorative against someone else. I made it up in 4th grade and everyone copied it. That makes them all dogalogs.
"You're about as useful as a dogalog in a swimming pool."
My mother was doogaloogin long before I was ready to work on the cattleranch, and not a day do does go by that I don't reminisce about her purty motherly face.