When someone is finally resting or accepting a situation, after they've been fighting it. (Based on their use on hospital patients, who may be fighting to pull out IVs or foleys, and so they put "big mittens" on their hands so they can't hurt themselves, and they finally fall asleep.")
"Is your friend still suing their landlord to get their deposit back?" "No, she's decided to let it go. She's sleeping with the big mittens on."
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.