You signed up for either a WordPress.com or Gravatar account in June of 2008. Account signups require email verification, so you (or someone with access to your email account) would have had to create the account.
Since we don’t want other people to have your username in the future, we don’t delete usernames (they are kept so they cannot be recycled). For more information, please see
I do have a few suggestions for you if you really want to scrub the account:
1) You can go to My Account->Edit Profile and remove all data except the account name and an email address. Create a throwaway email address and change the account email to that throwaway address. This only leaves the username behind.
2) To ensure the account is locked up tightly, visit this site, generate a password of 15-20 characters, and change the account password to it:
3) To learn how to hide your Gravatar profile, please read "How do I hide my profile?" section of the help page: