If you call a person an Ignoramus then you are saying that they are of low intelligence and applies little or no thought to a situation. In Latin, “ignoramus” means “we don't know [why this case was brought]”. The word was traditionally stamped on legal documents that were rejected by the courts as being badly thought-out and without basis. The expression has been in widespread use since the George Ruggle play of 1615 called Ignoramus in which the title character, a lawyer, demonstrated the ignorance of many of the common lawyers of that time.