A reference to Habbakuk 3:11 in the Bible, which Jesus alludes to in his triumphal entrance into Jerusalem (see Luke 19:40). Habbakuk is prophesying against the people of God and saying they've become such a bunch of self-serving hypocrites that even the stones and timbers of their house (figurative or literal) cry out against them.
If you want more explanation, I'm happy to unpack it more, but that's where it comes from.
As to why someone felt it made a good message for a rock wall? I don't know. Often Christians interpret it as the stones are crying out in joy at Jesus' arrival, but that misses the Habakkuk allusion, the political reality of Jesus' conflict with the Jerusalem temple authorities, and the context in which "hosanna" historically gets used.
I can understand but it’s actually rather poignant. The idea in scripture is that people are a bunch of hypocrites and worship the trappings of their religion rather than their deity.
That strongly parallels with Christian nationalism.