Celtics and Celtic hoops are not an uncommon soccer team name across the world. Most popular obviously is Glasgow Celtic, but there are even some American Celtic teams sprinkled across the Northeastern United States.
Jersey City Celtics lasted five games.
Brooklyn Celtic lasted several years (eventually transforming into Brooklyn St. Mary's Celtic) and even won a U.S. Open Cup.
Kearny Celtic is the most famous and succesful, lasting from the Great Depression well into the post war period. And, now there is a bit of rebirth of the Kearny club, playing in the Northern Jersey Soccer League as the Kearny Irish FC. They even draw their history direclty from the historic Kearny club and play in the same facility.
These folks really need to sell some t-shirts.
There are even Celtics in England and Spain.