Bored for the simples

An expression that you hear on the Lum and Abner radio show from time to time is, "I ought to be  bored for the simples." Taken in context, it must mean roughly, "I have been pretty stupid." Finding the exact origin of the language, however, has been a little more difficult. "Simples" was a name for herbs, and some have thought that it had something to do with that. Others say it meant to have a hole bored in the head to cure lunacy. Some say it comes from the practice of boring cow horns, which were hollow, indicating that a person's head was likewise hollow. Others say it indicated boring a hole in the head to let out the stupidity. One person even said that it should be spelled "board," but that seems unlikely to me.