Naming conventions of Primals.

[Enkidoh]

I don't think SE are really following any particularly deep naming convention for summons, given the fact with the exception of Good King Moggle Mog and Ravana, all the Primals are traditional summons from previous FF games (I'm not including the Warring Triad at the moment in this, as that is still for all intents and purposes just a set of immobile statues, and even they were from FFVI, albeit as a boss and not a summon) - it's entirely possible that the writing and lore teams probably just brainstorm ideas and settle on names that they feel fits the narrative.

Also it should be noted that Leviathan and Titan were originally planned for inclusion in version 1.0 but were never implemented due to the terrible earthquake and tsunami that devastated Japan in 2011 - SE felt that it was just too soon to feature them in the game after what happened. Hence Good King Moggle Mog was the replacement.

A final bit of obscure trivia is 'Zulvaan' was originally what the community mistakenly believed was Gaius's name (Azeyma only knows where players got that idea from), so I have my suspicions that 'Zulvaan' seems to be something of a placeholder name used by the development team. But I'm most likely wrong here.