However, having looked into this naming mix-up a bit more, I found this summary that goes into detail over the historic roots of these. Pretty curious, and especially how non-Germanic languages later also adopted natrium and such.
Oooh, I had assumed we'd known about K and Na long enough that they were just independently established names (even if amongst the youngest of those), I hadn't realised there was an active fight about it around the time of discovery.