I don't understand. Rationalism in the philosophy world goes back to Descartes. I think that's when it was an explicit school of thought, perhaps a hundred years later at the most. I also rather like the philosophy distinction between rationalism and empricism (strangely enough, the online 'rationalists' seem to be empiricists) since it's a division between traditions with differing but obviously valuable approaches to how people know things - rather than one side simply taking the name to claim some kind of high ground. The name actually illustrates something distinctive about each group's thought.