Muppet

n.

Heard in Waterford, Kilkenny, Sligo, Galway, Limerick, Dublin and Down

A derogatory term for a foolish or ineffectual person, implying a lack of backbone or self-determination.

In use

Shut up, yer only a feckin muppet

Posh English

Be quiet. You are merely a tiresome fool.

Same phrase, other counties