The Boston Celtics joined the Basketball Association of America (BAA) in 1946. In 1949, the BAA merged with the National Basketball League (NBL) to become the National Basketball Association (NBA). The head of the Boston Garden Arena Corporation that controlled the new Boston basketball team was Walter Brown. He decided to name the team the Boston Celtics over other choices such as Whirlwinds, Olympians and Unicorns. His reasoning was that "the name has a great basketball tradition from the old Original Celtics in New York. And Boston is full of Irishmen.". So now you know who to thank for not having a team named the Boston Unicorns.