Once upon a time, "responsive design" was know as "fluid layouts"...
Lol. I also think the same. But you know how it is with web guys and the new generation of developers. Buzzwords! Web 2.0, the cloud etc were all new names of old things that already predated them.
I guess it may be relevant to name these milestones to indicate a different way of doing things. If they called it "fluid", it wouldnt have gotten much attention as it is a thoroughly exhausted technique.
Various representations of System designs are also called "wireframes", these days (gag).
Back to the topic. Responsive design is a kinda fluid layout with the secret sauce being CSS3 media queries. They allow actual logic within the style definitions