When a web server has directory listing (indexing) enabled, visitors can see all files inside a folder if no default index.html, index.php, etc., exists.
If a file named password.txt is in such a folder, it becomes publicly visible.

Example view in a browser:

Index of /private/
[ ] password.txt
[ ] config.ini

When they click one of these results, they see a page like this:

Index of /secure_uploads

[ ] passwords.txt 12 KB 2025-01-15 02:34 [ ] extra_quality.txt 3 KB 2025-01-15 02:34 [ ] top_creds.txt 8 KB 2025-01-15 02:34 [ ] backup/

Inside password.txt, they might find:

When website owners misconfigure Apache, Nginx, or IIS servers, directories become browsable. A file named password.txt might contain:

Attackers can then use those credentials to:

Put together, someone using this phrase is actively searching for publicly exposed password files on vulnerable websites.