Here's a helpful graphic from the article.
One theory proposed by the article:
One major theory is that royalty during the Baekje period began using silver chopsticks as a way of protecting themselves from being poisoned by their enemies, as the silver would change color when in contact with a poisonous chemical.
Interesting thought. The article also lists several other theories, all of which seem to have a reasonable level of plausibility. I wouldn't want to steal all their thunder (and page clicks), so I'll avoid sharing those other theories and let you click on over to read more on your own. Just some fun stuff to file away in the "you learn something new every day" category.