Directly related:
* Terminus: The end point of something, a boundary, or a stopping place.
* Terminate: To bring to an end.
* Terminal: Relating to the end, or a place where something ends.
* Termination: The act of ending something.
Less directly related:
* Extraterrestrial: Beyond the earth, outside of the boundaries of our planet.
* Interminable: Endless, without a boundary.
* Terminology: The vocabulary of a specific subject, a set of terms used in a particular field.
Let me know if you'd like more words!