When Eisav came into the world, he was all red and hairy, yet he was not yet called Edom or Seir.  Why not?  Because something's name should refer to its essential content and not to superficial or incidental aspects.  Eisav’s hair was only indicative of his being completely formed at an early stage, so the appropriate name was “Eisav,” as Rashi explains – completely done (“asui”).  A person's name should penetrate to his essence, not refer to his appearance.  

However, Eisav himself did not look at the inner essence of things, but was caught up in their externals.  He “ate of this world and inherited Gehinnom.”  This led to Eisav selling his birthright.  When he was hungry he saw a pot of lentils and referred to its superficial appearance, “Give me some of that red stuff,” as opposed to its contents, lentils or beans.  He likewise looked at the birthright superficially, as a means of purchasing food, not as a conduit for the blessings of Avraham and a special connection with the Divine.

During this episode the Torah calls him Edom, referring to his own superficial appearance, not to his essence at birth – a completely developed person.  In fact, he revealed himself to not be completely developed; on the contrary, at his core was a real emptiness.  This is what the Torah later says (Bereishit 36:1), “Eisav is Edom.”  What seemed to originally be finished and complete proved to be superficial and lacking.   

Eisav realized that Yaakov grasped the importance of the birthright.  Therefore, he said to Yaakov, “What good is a birthright to me?”  Similar to the wicked son on the Seder night, we can infer, “to me” and not to you.  To Eisav the birthright was valueless; to Yaakov it had immeasurable value.