Clem

n.

Heard in Sligo, Cavan, Donegal, Mayo, Offaly, Longford, Meath and Galway

A foolish or ridiculous person.

In use

Yer some clem droppin' yer keys down de drain like dat!

Posh English

You are a proper nitwit for dropping your keys down the municipal drain in such a fashion.

Same phrase, other counties