The word "Poly" is a Greek word, meaning 'many'.
"Scriptura" is a Latin word, meaning 'scripture'.
Put these words together and we get the phrase 'many scriptures'. The phrase "Poly Scriptura" would therefore refer to exactly that; be it all the 66 books in the Bible; the Bible & other books, such as the writings of the early church fathers; or, as in the Youtube video, the many different available Bible translations.
I found the below paragraph on this site. The author is rebutting "King James Onlyism"; that King James is the only acceptable Bible version and "sola-scriptura", and that all other Bible versions are "poly-scriptura".
Most of the time, but not always, he tends to become agitated when I ask this, because it puts him on the defense. He is attempting to argue for God’s Word being found exclusively in one English translation. However, it is his burden to demonstrate with reason why I must abandon my favored, non-KJV translation because it doesn’t fit the qualifications of infallible, inerrant, and so forth. Now, he can chide and mock me by saying I believe in poly-scriptura not sola scriptura or what ever, but he is still in the position of establishing why his view of the biblical text is correct and mine is in error.