I mean it is an accurate description of it, so that might be a connection… but if you know the actual history of the term then please share

I don’t know why, but I never made the connection of this pose to the term “reared-up” (meaning ready to go/launch) until recently.

https://youtu.be/-t5S4BbVPOw

(Joke starts at 30sec.)

I’m far from knowledgeable about this, but the only thing I’m aware of that might disrupt determinism is quantum mechanics. Something about particles at that level not having set values until they are observed, making them truly random. I have no clue how that could lead to free will. We still have no control over it. It’s more like they are the base that everything else is determined off of.