Both the nickname "Celtics" and their mascot "Lucky the Leprechaun" are a nod to Boston's historically large Irish population, and also to the Original Celtics, a barnstorming basketball team that played in the early 20th century.

Why are they named the Celtics? When founder Walter Brown began the franchise in 1946, he had a number of options on what he could name the team before settling on the Celtics. A nod to the city's large Irish-heritage, Boston saw huge immigration from Ireland in the 19th century.