Anybody that uses the British Channel 4 program Father Ted as their guide to Irish society and culture understands that everyone in Ireland, including catholic priests uses the word Feck a lot. (along with arse and girls!)
But here is a piece of trivia that you may not know. Feck does not mean fuck! It is used in the same way:
feck off!
feck you!
go to feck'en hell
etc...
But it in fact is not defined as meaning sex or anything related to sex. The true definition is:
the bulk; the greater part; a quantity
-- dictionary.com
It has various meanings in different vernaculars including Irish English and Scottish English. So the Irish do not swear as much as Father Ted would have you believe. Feck is as wholesome as a good Irish Colcannon.