HALO stands for High Altitude Low Opening, but they weren’t wearing any 'chutes to be opened.
So as opposed to a HALO jump, as relevant as that might be as a pun, would it be more appropriate to call what Osiris did a HELL jump?
And just for the sake of making up words to fit the acronym, how about High Elevation Light Landing?
I mean, they did land lightly… relatively… compared to other Spartans we’ve seen drop from low orbit.
Title Edit: Thinking*