>>57963473The issue is mostly that in Japan, "irochigai" got used in marketing a LOT from the very beginning to the point fans never even considered coming up with their own different term for it. It's like how nobody in the west would ever consider coming up with a different fan term for "Gym Leader" since the official term is everywhere and so in their face.
But since the localization was so shitty back then, the localizers didn't even seem to realize there WAS a term to keep consistent, so it just got translated in various different ways whenever it popped up in the anime and ingame text. And that's why fans came up with "shiny" and the localizers eventually just said fuck it and made that official.
>cardsThe TCG equivalent has always been "Hikaru Pokemon" in Japanese and "Shining Pokemon" in English, and the similarities between the official "shining" and the fan term "shiny" is just an incredibly bizarre coincidence.