To clarify, a bit of SDA church history.
Starting in the early days of that movement it was considered an important piece of doctrine that the RC church was on the side of Satan*.
'Proof' that the papacy was the beast of Revelations comes in real handy if you take such a position.
So some people who by the standards of the time weren't very educated (they knew some Latin but no Koine Greek or Hebrew), started making up titles for the pope in Latin that sounded convincing to them.
Eventually they stumbled on Vicarivs Filii Dei.
Now they had to place it somewhere.
In the beginning they used the door of the Vatican. Later they used the pope's tiara (presumably because it is much more dramatic).
Eventually people started asking embarassing questions. So finally some real researchers had to be deployed to find 'proof' that Vicarivs Filii Dei was a real papal title.
They discovered that Vicarivs Filii Dei had been used by somebody else once before in the history of Christianity.
By the guy that wrote the Donation of Constantine in the 700's.
So this became the final version of the myth, Vicarivs Filii Dei is now supposedly a semi-secret title practically never used because it is evidence of the evil nature of Catholicism. And the Papist Pigs know it!!!
*Some cynical folks would see this
anti-catholicism as a manifestation of 19th century American xenophobia directed at the new waves of immigrants who were mostly RC, but let's not dwell on that.
