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>confusing irl inspiration and in-universe naming
Tera is a contraction of ステラ sutera/stella, the japanese name of Stellar type. Tera-type japanese name is even an anagram of Stellar type because they call it "terastype", with an s
>テラスタイプ terasutaipu -> ステラタイプ suterataipu
So the terastal phenomenon would be the "stella crystal" phenomenon which fits SV astral themes (see Team Star for more)