The over-use of Dungeon came at a time when the games were sold to kids. All kids knew was that dungeons were bad places to be.
I don't know if you are familiar with pencil and paper RPGs, but in this context dungeon really doesn't mean prison. There is a whole subculture with its own terminology, also used since the earliest days of computer games. Terms and concepts like NPC (Non-Player Charater), PC (Player Character), HP (Hitpoints) and many more were created. A DM/Dungeon Master is the guy who leads the campaign, not a prison (first introduced in Blackmoor, 1975). A Dungeon Crawl is a specific type of adventure, not a crawl in prison, etc. I'm trying to say, the use of "Dungeon", in the context of RPGs, is correct (even if it hurts the ears of history buffs
).
And in those early days, it wasn't sold to/targeted at kids btw., the audience were mostly teenagers and college students, but also older guys (Gary was 35 when he founded TSR 1973).
