I'm afraid this question probably reveals me as an out of touch, uncool curmudgeon with as much of a clue about pop culture as my ball python has.... but what's the scoop with the word "derp"?
This forum was the first place I encountered it, so I assumed it came about just because it rhymes with "herp". It appears to means silly or dorky, or maybe clumsy or dopey as applied to a spider with a wobble? But then I noticed it used in other places where there is no herp context that I can see.
So, errr, explain it to me? Or is this just one of those things that being over 30 disqualifies me from ever understanding?