I’ve long been aware that the Irish use feck a lot, and I had the vague idea that it was just a Hibernian equivalent of fuck. Not so! Stan Carey explains:
Feck is a popular minced oath in Ireland, occupying ground between the ultra-mild expletive flip and the often taboo (but also popular) fuck. … The most familiar modern use of feck is as a euphemistic substitute for fuck, as in the phrases Feck!, Feck off!, feck it, feck-all, fecker, feck(ed) up, fair fecks (kudos), (for) feck(‘s) sake, fecked (exhausted, ruined, in a bad situation), and the intensifier feckin’ or fecking, which often collocates with hell, eejit, gobshite or some such insult. …
Feck is family-friendly, even according to advertising standards authorities (though not always). As expletives go, it has a playful, unserious feel.
There are lots of quotes and lots of history, and a great Father Ted clip. Feck, er, check it out.