A hypothesis about the linguistic origins of AC & DC:
When electricity became a utility, we already had water conduits, gas conduits and sewer conduits, all carrying a stream of some sort. So it would be natural to have electricity be a stream supplied through some sort of conduit. Clearly, these conduits are adapted for electricity, and wires are generally preferred over hollow conductors.
One readily appreciates that a utility is delivered as a stream: water, gas and sewer are direct streams, but electricity has two modes, the direct stream and the alternating stream.
Compare this to other languages: when referring to wire, in German and Dutch we speak of "Stromleitung" and "Stroomleiding" respectively, literally meaning stream conduit. The conduits for water are "waterleiding" and "Wasserleitung" (... must remember to capitalize German nouns). Gas and sewer are similar. Equally, AC and DC refer to currents in these languages too, "wisselstroom" and "Wechselstrom".
And current is related to the French "courant", meaning "running", like a runner or a stream that runs. And the French "conduit" means to guide in this context, which is also related to our general term for the thing that "carries" electricity, the "conductor".
So it stands to reason that the thing of value that alternates along its utility conduit is the stream. Similar to other utilities, value is delivered when water or gas flows, not just when water or gas pressure is present. Also, billing is based on the amount of stream used (admittedly a very loose interpretation), not the pressure.
So perhaps it is the perspective of electricity as a utility similar to other utilities at the time, that lifts current over voltage as the primary source of value. And consequently the thing that alternates is the current.
Other languages do have a word for "alternating voltage" (e.g. the German "Wechselspannung"), and it is used when linguistic precision or a diversity of labeling is required to study and tackle electricity from a physics or engineering angle.
This is similar across Indo-European languages, but I'd be curious to know if other language families (Afro-Asiatic, Asia-Pacific families etc..) have a similar or different view.