Usually, the middle name in English culture is a connection with a past ancestor. For example, the middle name of my brother and my father comes from my great-grandfather. My own middle name comes from my mother's maiden name. My nephew has a Greek middle name, in respect to his great-grandfather.
That's usually how it works, but of course it all depends on the parents' choice. :)
Normally, we only use our middle name for administration purposes. Or if we hate our first name. :D