Musha
Heard in Cavan, Mayo, Galway and Roscommon
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.
The word Musha in English-'ish', is from the above Gealic words, generally used in sympathy." "E.g. To the baby, or young child who is sick or has hurt themselves..." "...'Ahh Muise'/'Ahh Musha' (It's the same pronunciation)." "Often used as alternative to 'There, there!' e.g. 'muise, muise'" "Or sarcastically, for ...'Sure, I'll play the fiddle for ya'!
The expression in question is derived from those Gaelic terms, generally employed to convey sympathy.