I think it all goes back several hundred years when "nicknames" were apparently widely used for children, no matter what they were christened.And many of them sound like babytalk, or the parent't imitation of it. I have seen "Hitch" as nickname for Richard,and the name "Hitchcock" meant "Little Richard." I have seen several others that I cannot recall at the moment.

After my above post, I was thinking that maybe there is no logic to it. And if enough people call me Bean, when my real name is Cristina, then maybe that will spread and in a couple of hundred years, people will be wondering how "Bean" came to be short for "Cristina". Ha ha!