This is likely the pseudonym of the individual who compiled, "cleaned" (removed duplicates/invalid entries), or leaked the data. Security Implications
If you are concerned your information might be in such a file: private gmail lines by xPainS.txt
Use a reputable service like Have I Been Pwned to see if your email has appeared in known data breaches. This is likely the pseudonym of the individual
In this context, "private" is often a marketing term used by data brokers to suggest the list is fresh, unique, or hasn't been widely leaked yet, making it more "valuable" for malicious actors. "cleaned" (removed duplicates/invalid entries)