Either way, this is a super cool project. You have to love it when someone puts their mind to it and produces something of this quality as open-source. I'm especially interested to see if this might kickstart some of the Rust efforts around GPGPU, which is currently so-so, since a cross-platform solution there seems like it would definitely be a benefit for this kind of project.
I looked at is as implying lightweight, nimble, and functional efficiency for small-scale uses, much like its namesake. I would assign much different metaphorical implications to something named "Zweihander" (Germanic two-handed sword) or an even more esoteric French polearm name such as "Bec de corbin" (a name probably only known to hoplophiles).
I hope I'm not misrepresenting your argument, but the way I understood it sounds very US-centered.
I know the word and its meaning and my initial reaction was negative because I thought "this has very little metaphorical value for a physics engine." You think of kinesis, movement, reactions. "Box" makes sense because it's a physical constraint with coming and interesting physics effects across its physics. Rapier is - to me - just an inanimate object.
But imagine you don't know the word. It could be jarring. And unlike words evoked by a sibling reply (paper, rap, etc) it's not nearly as commonly known or used.