Board Thread:Suggestions forum/@comment-30830745-20180225111723/@comment-26298013-20180228015227

Tolkien doesn't use the word "darts" exactly as we think of it. I always imagined it was used in the sense of just any old projectile. And the atlatl is a spear-throwing device. It throws spears.

Which Tolkien might of course be referring to as "darts".

Something I WILL complain about, though, is that if they were going over the walls they almost certainly weren't spears (range is too great), and the atlatl is a Native American weapon and not a common one at that, so we probably wouldn't see it in Tolkien's work. At least, not in the hands of Orcs or northern Men.