These fancy names are not Official Names.In fact those Admins who have perhaps named these trains are very much interested in Nomenclature so irrespective of knowing the significance of any place,they are naming the trains.
Dhulian stands no where near Bihar.It is aplace in Murcshidabad district bordering the India-Bangladesh Territory from where actually the River Ganges divides into two parts.The major part as Padma goes into Bangladesh whereas the minor part enters West Bengal as Bhagirathi(Hooghly).This train's route is no where near Dhulian