Why is a dependant clause also known as a subordinate clause?

Because it depends on the laws already at place

A subordinate clause: also called a dependent clause: will begin with a subordinate conjunction or a relative pronoun and will contain both a subject and a verb. This combination of words will not form a complete sentence. It will instead make a reader want additional information to finish the thought.

Aslender threadlike object or fiber, especially one found in animal or plant structures.