"Cager
A basketball player; derived from the days when a wire mesh barrier surrounded the court to protect the fans from the players and vice versa."
source
From a link on that page:
Quote:Basketball at one time was referred to as the “Cage Game” and players’ “Cagers”. This was a result of wire mesh (chicken wire) or chain-link fencing being hung around the entire court in an effort to make the game go faster by eliminating all the out of bounds delays. However, in reality, it served more as a barrier to protect the players and rowdy spectators from each other, as well as from the objects being thrown onto the court. The wire cage actually resulted in additional rough play with players body checking each other into the wire mesh as in hockey. Players often received cuts, bruises, and even incurred infections from the rusting wire mesh. Although, the use of cages were abandoned by 1933, the term "Cagers" is still used today.
There is an image of a "caged" court at that linked page, but i was unable to copy the url for the image because of the manner in which it is embedded.
Just because Joe hasn't heard of it doesn't mean it's not true.