"The choices of swearwords may sometimes seem illogical within a culture, but they are generally carefully selected from a specific set of taboo topics—forbidden acts, bodily functions, and human anatomy—because our natural offense at the subjects makes the words that relate to them the most obvious choices. American English curse words—motherfucker, shit, cunt—fall almost exclusively within these categories. These topics are used as the basis for swearwords because they are already imbued with some stigma. Over time, they are often abstracted beyond the point at which they are recognizable with the words from which they originated. For example, your mama, is a subtle reference to incest with one's mother. Fuck you, some linguists have theorized, may be an abstracted rape reference. Despite the fact that they are often not recognized as being related to the original taboos from which they originate, these words can reference the emotions triggered by the original taboos."

From the USC source referred to above