Castle Rock is the location of Shawshank State Prison in the TV adaptation https://castlerocktv.fandom.com/wiki/Shawshank_State_Prison
There are a few posts where Q simply states:
'CASTLE LOCK'
... instead of CASTLE ROCK, maybe locked up?
So maybe that's a reference to prison.
I don't think this is it, but I haven't seen this posted anywhere yet, so I'll drop this here. The Castle Rock Foundation was an American conservative foundation started in 1993 with an endowment of $36.6M from the Adolph Coors Foundation. "Promote a better understanding of the free enterprise system" "Preserve the principles upon which our democracy was founded to help ensure a limited role for government and the protection of individual rights as provided for in the Constitution" "Encourage personal responsibility and leadership" "Uphold traditional American values" The Castle Rock Foundation merged into the Adolph Coors Foundation on November 30, 2011.
https://en.wikipedia.org/wiki/Castle_Rock_Foundation