(not Fall Out Boy fob but Fresh off the Boat fob)
I discovered the term “fob” in my first year of high school. It was used to describe people who came from foreign countries, immigrants, someone who was fresh off the boat. As locales of another country, fobs have a culture that differ from the majority, a language or lingo that is their own. They have something that makes them undeniably distinct. From my understanding and experience on the other side of being a fob in high school, I did not see being a fob a bad thing. It was an adjective I used, we used, to describe someone or something.
Person 1: Which computer lab are we meeting in?
Person 2: The one next to the fob hallway (fob hallway is where the fobs hung out)
Person 1: You look really fobby today. It's cute.
Person 2: Why thank you!
urbandictionary.com - Looking through a few pages of definitions that random people have posted, I noticed that quite a few of them linked the terms “derogatory,” “degrading,” and "racist" to fob. In America, fobs are Asians and Mexicans; while in Australia, fobs are Pacific Islanders.
Wikipedia – “terminologies used to describe immigrants that have arrived from a foreign nation and have not yet assimilated into the host nation's culture, language, and behavior”
Yahoo Answers - "It means 'Fresh Off the Boat'... It's derrogatory."
So back to the question... a fob is (commonly) an immigrant with a cultural background that differs from the status quo.
(i know it's vague, but it'll suffice)