Interesting that the word comes directly from the Catholic Church, because I don't think they ever allowed it to exist.

When you see it happen in society, it's almost always learned from a military group or earned by some popular revolt.

It's interesting, I'm one of what I presume is a small number of people that have conversed extensively over my life about subsidiarity, mostly on the context of subsidiarity and sphere sovereignty a rather niche area of theology.

Most Catholics, even highly engaged western catholics are not aware of subsidiarity. It's ~commonly/known term and catholic juxtaposition cited by theological/historical non-conformists in church polity and discussions around separation of church and state.