Why the "Z", though? Well, leaked teasers for the Flip showed two phones, upper half next to lower half, worthy of a Zoro sequel poster. That's a deliberate strategy, and could either hint at future bi-folders, like the one Xiaomi demonstrated last year, or simply denote Samsung's handsets with a horizontal hinge, instead of a vertical one like the Galaxy Fold.
In any case, after the Galaxy S20 Ultra leaked in the flesh for the first time, and the Galaxy S20/S20+ naming scheme was confirmed, too, now Samsung reveals that it will indeed call its upcoming flip phone the Galaxy Z Flip.
It makes perfect sense, and there will even be an official case for it, as you can see from the telltale screen snaps from Samsung's Romanian (via PlayfulDroid), Swiss and French websites support section below.