To understand this joke, you have to know that men from Derry are a bit workshy. I have no experience of this, but if you believe it, it will make this joke work for you.

In the middle of the afternoon, a Derry man was sitting on a barstool sipping his pint of draught Guinness. The door swung open and a little guy minced in. Blonde curly hair, tight fitting pale grey suit, lavender shirt and pink tie. He went up to the bar and ordered a pink gin, in a cocktail glass with a cherry on a stick. He climbed onto a barstool at the end of the bar where the Derry man was sitting. They both sat there for over half an hour with no one speaking. Then the curly haired guy slid off his stool and edged up to the Derry man. He leant forward and whispered into the Derry man's ear, "Do you fancy a B/Job?"
The Derry man was off his stool in a flash. Hit the curly haired guy such a punch that he flew across the bar and crashed into the dukebox. The Derry man was after him, swinging his boot at the wee guy, who was running as fast as his wee legs could carry him towards the door of the bar.
The Derry man went back to his seat at the bar and continued to sip his pint. The barman approched the Derry man and nervously asked, "What was all that about, Paddy? What did the wee guy say to you?"
The Derry man replied, "Ah couldn't tell you for sure, but I'm sure he mentioned a job."