Yes this is another attempt to understand CASTLE_ROCK. No this is not another reference to a movie prop.
I don't feel that the movie idea is leading us down the correct path. Nothing on Drop #4414 scream out "Find me in a movie" https://qagg.news/?q=%23%234414
At first I felt that the term CASTLE is being literal. As in a Castle or fortress. Note: The cabal has been encamped in their "FORTRESS" for a very long time.
An underscore symbol can have a few meanings. It could join words, show importance to the word it is in front of, or can be used as the actual word and underscore by playing background music (fits the movie prop idea).
The word rock has a few meanings as well. It could be an actual rock/stone, reference Dwayne (THE ROCK) Johnson or mean to move/sway/shake violently.
I searched for under ground castle/fortress (found an old nuke silo turned into a Air B&B in Kansas - added to bucket list) and really couldn't find what I was looking for.
I also found a drawing made in 1873 of Castle Rock WA. Doubt that was it either.
I searched qdrops for other references to both words. A few Castle drops talked about building the boarder wall using the Army Corps of Engineers (RED/GREEN Castle).
I think CASTLE=ARMY
Replace every instance of castle with army.
CASTLE_ROCK = ARMY_MOVE
The most infamous reference to Castle Rock would be the direct reference to the location of Jack's fort (stationed with his hunters) in the novel The Lord of the Flies. The very Castle Rock for which the studio is named. Castle Rock is both a good place for a fort, but is barren of life and hospitality. Sounds a lot like a swamp I know.