No, you will need to use one word, I believe that the manual will also explain the maximum character length as well.

I understand the need to customize the login accordingly, But the only alternate would be creating FTP directories if needed that way they can simply access through an FTP client using of course explicit TLS  connection for security purposes.

If, you can provide more on what you want to do maybe I can provide some suggestions.

From viewing your other posts that are similar to what is posted here, I would suggest using some open source script that allows logins for private areas. This in turn allows them access to their own account so to speak or what you prefer them to have. I cannot think right off hand scripts like this at the moment. I am kind of out of touch on what is out there for such implementations. As MrPhil suggested in one of your other posts, I would suggest looking into a membership script that way you would resolve all of the issues at once with password protect for directories. There are tons of membership type of scripts out there which would fit your criteria for having a specific customization to it.