Taking leaked data from one site and testing it against another (like Gmail).
Using malware to grab passwords saved in browsers. The Risks for Users Taking leaked data from one site and testing
The phrase "Private Duplicate Removed" is a marketing tactic used by data brokers to suggest the list is unique, high-quality, and hasn't been "burnt" (detected and blocked) by security systems yet. How These Lists Are Created Taking leaked data from one site and testing