I see.
I expected they would have used other verified 'named' Solar System objects before inventing a name for the hypothetical Planet X.
{ i.e Uranus, Neptune, Pluto, Ceres, Sedna, Eris, Makemake, Orcus, Gonggong ... }
But Artemis is just as good I suppose. ( actually sounds better than some of the more recent goofy names chosen by IAU. I admit, I am biased toward the established Grecco-Roman mythos naming convention. )