Guidance to officers in the Police Service of Northern Ireland --
Catholics should not be called fenians, taigs, chucks or spongers, while Protestants should not be referred to as huns, black, prods or jaffas, the booklet says.
There is one exception to the use of fenian, but it is probably rarely used. "It may be perfectly acceptable to use it in an appropriate historical context, for example, if referring to the Fenian Brotherhood," it says.
For example, indeed: "He's one of those people whose ancestors might have been in the Fenian Brotherhood".