[1970s] (US) an Irish (and Roman Catholic) person.
SE in slang uses
[1990s+] (Ulster) a Roman Catholic.
[mid-19C] the lymphatic gland surrounded with fat, found in a leg of mutton.
[late 18C+] the rump of a chicken or turkey.
see does a bear shit in the woods? Is the pope (a) Catholic? phr.
see put the devil into hell under devil n.