Otaerd is people who are nerds (Like they are so intelligent but unpopular i.e. people with big glasses and neat hair) and an otaku. Otaku is a Japanese word meaning people who loves japanese comics (but you would never call people otaku if they are not really reading comics but just a little.) Otaku people will often go to akihabara and often are men probably around their 20s~30s and would be always apear in books that they have glasses on and are fat. So Otaku and Nerd is mixed in this word. = Otaerd (pronounced otardo)
Boy 1: Have you heard of the manga (japanese comic) To love ru?
Boy 2: Oh yes! I read it with my best glasses on and searched in the dictionary what all of the words meant!
Girl 1: Oh my god! You're such a Otaerd!
Girl 2: Init! you're a nerd and You're an Otaku!