Um? whats a dueche bag?

Or how ever you spell it.. anyways, when i was in 6th grade there was a boy who sat next to me everyday in math, every single day he would call his friends d-bags and one day i was kidding with him and called him one and he litteraly fliped out on me, he was sayin "GIRLS DONT SAY THAT!! WHY WOULD YOU SAY THAT OH MY GOSH DONT SAY THAT EVER AGAIN!!" And i was like geez okay? i was just kiddn and i didnt know what it ment so i just said it... but anyhoe, obviousley its dirty, and idk what it means, so! someone explain :)