The original intent of this word was to be a shortened form of dickweed. By using the word dweed, they were able to call their classmates derogatory terms in front of teachers with no repercussions.
Because only a select group of students knew what was actually being said, the word was mispronounced in abundance, causing the word to involve dweeb.
"I'm not a dweeb!"
Can be used as a derisive term for a person in the sense that you're calling them a "thing".