I wouldn’t say it comes from Korean, more like it and its analog in Korean probably have a shared origin due to the mixing of ancient Koreanic and Japonic peoples pre-migration and during migration. It may have come from a different language that doesn’t exist today, it may have originated in proto-Korean or proto-Japanese, or Koreanic and Japonic language speakers may have just changed each others language in a way which caused the particle to emerge in both languages (which is certainly plausible given how much they influenced each other’s grammar in general).

So you’re saying it still could’ve come from Portuguese??