Definition & Meaning of "final frontier"

What is the origin of the idiom "final frontier" and when to use it?

The idiom "final frontier" originates from the context of exploration and discovery, most famously popularized by the television series "Star Trek" in 1966 with its phrase "space: the final frontier." Historically, a "frontier" refers to the edge of settled or explored territory, representing the boundary between the known and the unknown. As human exploration advanced from lands to oceans and skies, space became seen as the ultimate challenge, or the "final frontier." Today, the idiom is used to describe the last or most challenging domain to be explored or understood, symbolizing the ultimate goal or limit of human endeavor, such as in fields like deep-sea exploration or neuroscience.