Said in response to someone saying thanks. Comes from a Joke where David Hasslehoff asks a Clerk to change his name to the Hoff... when the Clerk said Sure, No Hassle. Now instead of saying "No Hassle" people just say Hoff.
This is a very, very common thing amongst Irish people when describing a person, place or thing. Because sometimes we can't articulate how large or small an object is, or the skin tone of an individual or even the heat of a local curry dish - we use this a lot! We basically just say the word twice and the person who gets the info knows exactly what we mean by tone alone.