: Check if there is a ReadMe.txt or a .url shortcut included in the folder where you found the RAR; these often contain the key. Technical Identification

: Try the username of the person who posted the file.

: Be extremely cautious of sites claiming you need to download a specific "cleaner" or "unlocker" tool to open this file; these are frequently used to distribute malware.

If you are trying to open a .rar file with this name or password, here are the most effective ways to proceed: Common Sources for RAR Passwords