The word "underlying" comes from the verb "underlie" which is a combination of the prefix "under-" meaning "below" or "beneath" and the verb "lie" which means "to be in a certain position" or "to be located." It was first used in English in the 16th century to describe something that is located or situated beneath something else. It is derived from the prefix "under-" meaning "below" or "beneath" and the verb "lie" which means "to be in a certain position" or "to be located." The adjective "underlying" is used to describe something that is located or situated beneath something else. It can also be used to describe a hidden or underlying cause, meaning a cause that is not immediately obvious or visible. It is often used in various fields such as science, medicine, and psychology to describe something that is fundamental or that provides a foundation for something else. It is commonly used to express the idea that something is located or situated beneath something else, or that something is a hidden or underlying cause of something else.