Named with direct current because of the current direction always flow on one direction. The current flow will fix if the voltage and the resistance also fixed. If electric current is one-volt flow on wire with resistance 1 ohm, so the current will flow 1 Ampere.
If that current flow through fixed wire, the magnetic field in surround wire also fixed, as the conventional agreement, direct current flow through positive pole to negative pole.
The direct current flow is always same on the same wire. The current flow merge if on the electric source have electric on their pole or no movement. On this condition electric source that exist because of chemical action like on the wet element or dynamo that accomplished with current commutate can resulting direct current.
Say with dry elements or dry cell because of this elements don’t use fluid, otherwise use electrolytic paste instead of liquid chemical. Dry elements work base on the depolarization. As the depolarisator is mixed of mangan dioxide (MnO2) with carbon dust that function to omit the gas bubble (hydrogen) on positive electrode. On daily activity, dry elements known as battery.