[Regalia], [Astra], [Icon] and [Avatar].
In order, these are the tiered, exclusive abilities for aether warriors of the Grandmaster, Lord, King and Emperor levels.
But where did these names come from?
To be honest...nobody knows.
Cultivation, especially aether cultivation, has always been a part of people's lives for so long that the humans, the Bloodliners and even the Aetherii have all collectively forgotten the originator of certain names of the trade.
That stated...I have a theory on why these terms are used.
Much in the same way a certain country uses Jell-O to refer to gelatin dessert or Q-tips for cotton swabs, I believe the terms of [Regalia], [Astra], [Icon] and [Avatar] were all originally coined by one warrior and everyone else just sort of...picked it up.