Fun thread, just found it! Back when the internet was young and my rural area first got dial-up connection, we signed up with a small mom-n-pop server (I could often hear their kids in the background when I called for tech support). At that time, the four of us (me, husband, two then school age sons) were totally clueless about computers but ready and raring to try out this new wonder. We were told to come up with an 8 character password we could all remember. After much stewing, we decided on Bonehead - the required 8 characters, easy to remember, and no question about the spelling. As we worked our way through the sign-up process, Bonehead was mistakenly entered as our user name rather than the password, which we all found ironically funny. So we just stuck with it. I like to think we all have our bonehead moments, and embrace my screen name as a reminder to keep things in perspective.
P.S. Unfortunately, Bonehead is now most often already 'taken' so if you ever run into Boneheadeb on random sites, that is me as well.