Very interesting. Qursan seems one of those old words that existed forever, especially that it described a phenomenon mainly associated with the past.

Also of major importance is the fact that the word originated in North Africa. Middle easterners tend to treat Northern Africans as mere users of the Arabic language who are forbidden from contributing to it. This is a reminder that this can't realistically be accurate.

Also, I think qursan has a four-letter root (rare but not uncommon): q-r-s-n.

I can’t help but wonder why qursān ended up being the final form instead of qursāl.