Wow. We had a thread like this how long ago? Two weeks?
Aside from Ansem's Apprentices and Roxas, the others we don't know about. For all intents and purposes, they might not even have been made with original names in mind.
Lumaria is popular for Marluxia, since it is the name of an actual plant.
Elenar is popular for Larxene, given that it's almost the same name of a blonde, female, Final Fantasy character. Narele is also a possiblity, and a name spelt similarly to how it actually is spelt.
Axel's name, minus the 'x', spells Ale, the favourite drink of Reno, the Final Fantasy VII character from which Axel was greatly influenced. Going for a real name, Lea seems the most likely.
Not sure for Saïx, but Sai is the name of an actuall weapon, and sounds better than Asi and Isa and the other variants to me.
Luxord might be Dolur, given his associating with money and being a gambler.
Not sure for any decent link between Demyx and any name he might have had.