"quorum causam" would still make sense if we take "causam" as the cause/goal for which they died [he died a martyr for a good cause]
I'm just wondering whether one can get "whose cause" in this sense from the Latin as it stands - cuius causam.
I've just read this and thought about this question of yours. Here causa seems to be used in that "good cause" sense:I can't say for sure, but I've never seen it in any case.