Forget the "current" part of the phrases "direct current" and "alternating current". Current only flows when we have a closed circuit. The terms are labels that come from a description of power circuits, one having fixed potential and therefore fixed current when loaded, the other having a sine wave output, and therefore an alternating current when loaded. But when we talk about potentials in general, we almost always refer to a steady potential as DC and a moving one as AC. That's the part to focus on, whether the potential is fixed or moving.