It atleast seems that way from the way he talks about it. Part of me says it sounds weird and that Zaunite is better, but another part of me digs it. I dunno, what're your thoughts guys?
Windfallen3 votesMy speculation is that Ekko is just using his own terminology. Whether Zaunites themselves or people on the outside use the established term "Zuanite" doesn't matter to him.
To him, if you come from Zaun you are a part of it as much as it's a part of you. You're Zaun.
EDIT: Further speculation is that it's also an endearing slang word/title. Since the interactions with Vi/Viktor.
@ Vi: It's like he's recognizing her for it and not just categorizing her as just another "Pilt-y".
@ Viktor: He's gotta prove it as if it's like a title to be proud of.
Sharjo1 votesThat makes sense. I guess we could stipulate that "Piltie" is something of his own design as well, though I feel like that works better as traditional slang anyway.
Well regardless I'ma ask them in the inevitable Ekko Q&A. I'm still not 100% on this!
Windfallen1 votesIt's a good question!
Ebonmaw Dragon2 votesZaunite is the demonym for the people of Zaun, the word is used alot in the old JoJ, also in the lores of Jayce and Ziggs.
Sharjo1 votesThen why the phrasing in Ekko's lines such as:
To 
: "You'll always be Zaun to me."
To 
: "Think you're Zaun? Prove it!"
I dunno. I'm just awfully confused about it.