I'm just guessing here, but maybe that's what the question eludes to?
Seriously though, if you ask probably a solid quarter of reddit's user base about trebuchets, they'll probably be able to recite from memory: "a medieval siege weapon capable of launching a 90kg projectile 300m". Don't question it, the internet is a strange place.
And personally I think it is kind of weak to call people cheaters just because you yourself havent heard of a word. If that many people cheated on this quiz, the average wouldnt be as low as 15 (I would have thought it would have been higher, the question werent really tough)
Plus anyone that has watched myhtbusters will have come across it multiple times. Or anyone that likes davinci, or middle ages in general or physics or... well there are tons of ways to be exposed to the word.
You arent totally wrong though, quarrels are bolts that are used for crossbows (still bolts though) , they specifically refer to the square shaped ones, recognise the word quadruple/quadrant in it? It means 4 sided (square)
I actually only missed the last two ! (and I still see it more (in my head) as warfare terms or combat)