Galloping knob rot

phr.

Heard in Cork, Tipperary and Limerick

Infection of the male genitals caused by rampant stupidity.

In use

You've obviously got galloping knob rot, ya' Langer!

Posh English

You have clearly contracted a rampant infection of the male member brought on by spectacular idiocy you utter ninnyhammer.

Same phrase, other counties