Well , in answer to your last point yes actually.
There a document from Cambridgeshire constabulary freely available on the net which says as its 1st paragraph
"We recognise that in policing, we tend to use many acronyms and other jargon terms. To make this easier for you to understand, we have made a jargon buster to help you identify some of our language."
There follows a long list in Alphabetical order of such jargon one of which is......
CHIS Covert Human Intelligence Source
And Dunbar said he uses' Mother of God' and others because his father used to use them. Other phrases are Belfast phrases that he knows and uses. Some are from Q and A sessions wth Belfast audiences. He is of course Irish himself ( from Enniskillen) so he should know!!!!!