No Dinah's the cook. There is the line earlier which goes "... Dinah blow your horn" ie. the dinner horn to call in the workers to eat. My husband and I sang "I've Been Working on the Railroad" just recently on a tourist train. He learned it as a child in America. I'm Australian so I had always thought that the horn was somehow on a train and that Dinah was a train. It always puzzled me too. My true-love set me straight. Joy