Yes, it is named after a former player. The account was deleted a few years before the duchy was named.
In this case, I would think that the name does not violate the sprit if the rule. The intent of to prevent the frequent renaming of duchies every time a new Duke is appointed. Duchy names are not vanity titles. Every new Duke shouldn't get his duchy named after him.
The Primus duchy is probably OK, as it is named after a historical Sirion figure, not a current player.