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.
Muise; Indeed
(b) Muise! Muise!; Well, Well!
Muisiam; Upset.
Muisiamach; 1. Upset; perturbed; irritated.
2. Feeling sick.
3. Heavy / drowsy / dull.
(There is a "fada" over the "u" in each of the above.