The word "anal" refers to anything related to the anus, which is the opening at the end of the digestive tract in humans and many animals. In a more informal context, it is often used to describe someone who is excessively meticulous, overly organized, or rigidly controlled, a trait sometimes termed "anal retentive."
The term "anal" comes from the Latin word "anus," which means "ring" or "circle." The anatomical term has been adopted into English, often with additional connotations growing from psychological theories related to personality types.