Derived from the word "idiot". Someone who mistakes the obvious so often that those around him/her do not go even through the trouble of calling them the three-syllable word "idiot" anymore.
"So Julius Caesar invented the Caesar salad AND ruled over the Roman Empire?"
"Wow, you're such an id."
Derived from the combination of the words "loser" and "boob". Someone who has no sense of reality, or social skills.
That loob just spent his passing period arranging his pencils in color-order before the test.