When I was about 9 years old, I started working as a farm hand doing manual labor on a pumpkin patch that a family friend owned. I had to do such things as pick/shuck corn, clip fields of pumpkin stems, and pick trailers full of pumpkins/gourds/squash from said fields, etc. Well if you've ever walked in a pumpkin patch, you know that the vines are everywhere, and for the first month or two, I couldn't walk through those damn fields without tripping and "Skipping" all over the place. Thus, the nickname Skippy came along.
The number "4" came about in 2004 when I was creating my AOL Instant Messenger screen name. It was going to be Skippy04, but that one was taken at the time, so then I tried Skippy004, and that one was taken as well. So I skipped the third zero and went straight for the fourth.
And my interweb alias was born.