Capture The Flag is a cybersecurity game where the organizers set up a bunch of intentionally vulnerable computer systems with a "flag" on them, a string that's "supposed to be" secret but is accessible through exploiting the vulnerabilities. This may be a line in /etc/password, a string in memory, a field in a database, whatever. The goal of the game is to hack into the computer systems, find ("capture") the flag, then copy/paste it into the organiser's scoreboard website to prove that you solved that particular challenge.

It's pretty fun. Or at least it was, back when you had some sense that your competitors were competing on an even playing field and just beat you because they were better than you.

I wouldn't say the name is a "gaming reference", it's just a descriptive name for a game.