It's Intel trying to catch on the whole Apple trendiness bandwagon. Basically you stick an 'i' in front of everything because that allegedly makes your product cool.
I recall it being posted somewhere that the *i#* has no real meaning other than representing it's an intel processor and generation and where it's placed on the hierarchy of intel CPU's.
Most people assume the *i* stands for intel but i don't recall it really means anything.
iPhone, iPod, iPad, i3, i5, i7
It was to mark their 'new series of chips' but it still only stands for intel.
I would assume that it stands for intellegence because their new CPU's have dynamic overclocking which only uses the overclock settings when under a big load. It could be said that it intelegently picks when to get faster and the number stands for the classes like i5 has normal turbo boost and i7 has turbo boost 2.0 which is supposed to make it out perform i5's with the same Gigaherz speed.