Attempted attack how could they have snooped my user name?

Greetings,

I am puzzled. I just noted somebody (from Russia) tried to log in. Now I see attacks from time to time on this domain (it is under construction and has a note to that effect), but what worried me is that his individual had my user name almost correct. Except for some upper case characters. In other words correct but he used lower where it should have been upper case. How could they have found out? Now I haste to say that as the only admin of the site, I use a user name of random characters (upper and lower case) with special characters in between, over 20 characters long. So the changes of guessing are so remote I do not think one could in 20 years. Especially since my security settings throw you out if you use one that does not exist, so no trial and error here and fishing if you got it right. I also always log in over a secure connection.

Does anybody have any hints as to where this individual could have possibly found out? Is there a hole somewhere? Any insight?

Thanks.