Multi-factor authentication is the strongest defense. Even if someone has your "valid" password from a combolist, they won't have the secondary code needed to log in.
The phrase sounds like something pulled straight from the underbelly of a data breach forum. While it looks like just a file name, it represents a significant threat to digital privacy. The Anatomy of the File 145K: Refers to 145,000 individual entries.
A marketing term used by hackers to claim the data has been "checked" and currently works.
A "combo" is a list of credentials in username:password format, often compiled from multiple different website leaks (the "mix"). Why This Matters