|Photo by Tommy Hancher|
Geek traces its origins back to 1510, surprisingly--and was even used by Shakespeare! The meaning has changed over time, though. Originally it meant "a fool, a simpleton." Within twenty years, it was applied to contemptible people in general. In the early 1900s the circus folk adopted it to mean "a sideshow freak." Still, it took quite a while longer to be applied to that particular brand of person awkward in the social graces but up on computers--our geek didn't gain the name until 1983. So this is a word both very old and very new!
Nerd is even funnier. It's thought to be a variation of nert, which was 1940s slang for "stupid or crazy person," but it didn't really gain in popular use until Dr. Seuss used it in "If I Ran the Zoo." Seuss's nerd was a small, unkempt animal, and that, interestingly, is where the modern take comes from.
And now they both have such particular definitions that each will proudly claim his own title but be very offended if you call him the wrong one. ;-)