term used to show up those who call you a "smut muffin" thinking you're too blonde too figure out that its an insult. tums is simply smut
backwards, and cupcake is just a way of mimicking the "smut muffin
" phrase and one uping it by adding frosting. "tums cupcakes" are generally people too sheltered or stuck up to realize how obvious the insult is, and are usually the aggressor of the situation, calling their victims smut muffin freely not aware of the consequences.