francis' papal name is in honor of a saint. this is an example of the first scenario.
You could chop up any regnal name into a good sith title because the language of the Romans naturally conveys power and authority. Some other examples:
Talionis
Anteru
Xystus
Severin
All Sith are given Sith names that are completely different from their real name
Brandon Peterson
Jose Hall
"Severin" seems a little on the nose, but I suppose this is a universe with a character named Savage Opress.
Justin Powell
>Darth Severin
Apprentice to Darth Siouxsie?
Elijah Collins
This
Jack Harris
Revan and Malak are not their real names. Nobody knows Revan's name, but his sith title was adapted from his position as unofficial head of the Revanchist Jedi who went to war with the Mandalorians.
Malak's name is like, Alek or something. Really boring.
No more than "Sidious" or "Tyrannus"
Ryan Foster
adding to this star wars fans are all shallow pieces of shits and are on par with the sonic fandom
Connor Diaz
His real name was Icky, first name Darth.
Camden Jackson
Isn't Revan canonically female? Wait, maybe that was Revya.
Michael Adams
Nope, shes officially a sith
(This is just one example and im at work so I wont have the opportunity to reply with more official examples until later on)
Jack Adams
Why is that her mission?