What's in a name?

I've posted before about what I have referred to as the "National Insurance Scam" (see post of 24/2/10), and now at last an MP has taken up the cudgels.  A Bill is to be introduced to rename the levy as the "Earnings Tax" on the basis that, as I have said, it is not and never was insurance as commonly understood by the man in the street. Mind you, what exactly is the difference between "income" and "earnings" when it comes to tax is not readily apparent, and I do wonder if what is behind this is to pave the way for the eventual merging of the two, which has been talked about more than once.