Green’s Dictionary of Slang

moriarty n.

a party.

1992		R. Puxley Cockney Rabbit.
2017		(con. 1950s) Spitalfields Life 30 May 🌐 Those years that we lived in Northport St were the years of the parties at our house, where people would come out of the pubs, carrying the booze home, having a ‘Moriarty’ as it was known.