Mine is easy to explain.

I used to be known as KeithW but I visited a numerologist who explained (and showed me) that if I used the name KeithieW I would have a happier time of things. So I've been known as Keithie ever since.

Also, and this is probably more plausible to a lot of people, one of my aunts visited the day after I was born and said "Hello Keithie Weithie".

Everyone has called me Keithie for years and I love it.