Here are some quotations from
http://www.wisegeek.com/what-does-it...u-go-dutch.htm:
The origin of the phrase "go Dutch" or "Dutch treat" can be traced back to a time when England and the Netherlands fought constantly over trade routes and political boundaries during the 17th century. The British used the term "Dutch" in a number of derogatory or demeaning ways, including "Dutch courage" (bravery through alcohol) and "Dutch treat", which was actually no treat at all. The Dutch were said to be very stingy with their wealth, so the British used the word "Dutch" informally to imply all sorts of negative behaviors.
The modern idea of "to go Dutch" no longer carries the stigma of the term's original intentions. It is simply a recognized bit of social jargon which allows each party to know the financial arrangements of a date or social outing before the bill arrives and allows each party to spend according to their personal entertainment budget.