The most simple, straight activity can carry powerful erotic overtones. I read of a female submissive given a task. Go to the grocery, purchase the largest cucumber she could find, a roll of duct tape, and a bottle of personal lubricant. The check-out was crucial. The cashier must be either a younger male, or a matronly female. It was that simple yet profound.
There would be an obvious assumption. It is the public exposure, an intimate revelation…especially when approached directly without explanation or comment on usage. Public exposure of erotic intimacies, especially if the submissive is required to play straight, is very erotic.
For a male submissive it could easily be a trip to the intimate apparel section of a store and the purchase of those panties and nylons the would just happen to fit. The exposure of the socially effeminate stereotype is a truly erotic humiliation.