Well, you know the background of my nickname, LuLu (which also happens to be the name of the blog...).
A long time ago, I called a guy friend of mine "Jill", and he called me "Fred"....and the nickname "Fred" came from my friend Megan ("George")....for no reason that I can remember!
And....my dear friend Kathryn called me "Joe" one day, and I called her "Peaches", and....that stuck. (Again, for no apparent reason)
And....my nickname, Rae--which I often feel is more my name than Rachel--is family-originated. Started with a relative, Anna Rebecca, being called Rae for short, and then my aunt Rachel was called Rae, and so...I am Rachel, called Rae!