Spanish nick-names

I was always under the impression that a nick-name is a short form for a name. Eg. Robert = Bob, Frederic = Fred, Philip = Phil, Matthew = Mat.

But in Spain they are on bit of a different wavelength:

Enrique = Quique (ok, not bad)
Francisco = Paco (huh?)
Jose = Pepe (??)
Maria Carmen = Mamen
Rosario = Chari (HUH?)
Ignacio = Nacho
Joaquin = Ximo

And how did the whole of Spain or Hispanic world decide to come to a unanimous decision? I'm sure there are plenty more, how do you remember them when they are so non-corresponding? And why bother naming someone Jose, if you are going to call him Pepe? What about poor Pepe? Are all Pepe's Jose's?

Yes, I have had a long day. Guess some things are better left as they are.

Actually, when you think about it Indian's are no better. Almost all of us have a nick name with no logic and no uniformity, totally random.

For eg.
A Sneha could be: Pinky, Micky, Minni, Choti or Rani
A Nilesh could be: Nilu, Bittu, Shanu, Monu, Titu or Lovely.

No , I don't have one. Thank goodness.