A Liverpool Football Club supporter, brother of Blogger: From the point of view of an Arsenal fan who subscribes to Arseblog. Blogger's brother (being a Liverpool fan) allegedly smashed Blogger's Arsenal mug when they were kids. Mugsmashers is now a common collective term used to describe Liverpool football club, its supporters and the city in general.
A sunburn or suntan focused on the left arm. It is caused by the left side of the body being the only half that gets exposed to sunlight while driving. Presumably, it would be located on the right side of the body in countries where they drive on the left side of the road.
British slang for a scientist or technical expert, esp . when the speaker is not certain of the expert’s specific field of study. Not necessarily derogatory, but typically used by persons without a technical background. In the US, the equivalent would be “egghead”, “squint”, or “geek.”
Origin of the word is unknown. Started sometime in World War 2. Given the typical evolution of British slang, could easily have started because what these experts did was confusing or “baffling” to the common person.