Where does “ないちゃあ” come from?

ないちゃあ (Okinawan) comes from Okinawan あー, from Proto-Ryukyuan *awa, from Proto-Japonic *awa — bubble.

Ancestry of “ないちゃあ”, step by step

StepLanguageWordMeaning
1Okinawanあーbubble
2Proto-Ryukyuan*awabubble
3Proto-Japonic*awabubble
Every word from Proto-Japonic *awa →Every word from Proto-Ryukyuan *awa →Every word from Okinawan あー →
ないちゃあ — Etymology, Origin & Word History | Etymology Explorer