 BJs real name is never given. In one episode, Hawkeye goes to  extreme lengths to learn what "BJ" stands for, but all official  paperwork concerning his friend claims that BJ really is his first  name. Toward the end of the episode, BJ explains that his parents  names are Bea and Jay, and claims that this is the reason for his  odd name, but whether this is actually true is never made clear.