What does 'first estate' mean in Jude 1:6 (KJV)? Jude 1:6 (emphasis mine):


  And the angels which kept not their first estate, but left their own habitation, he hath reserved in everlasting chains under darkness unto the judgment of the great day.


This verse references a topics that are not thoroughly covered in the Bible (Enoch, Michael, etc). I haven't found the term 'first estate' in the Bible anywhere else, and other translations don't provide much clarity for me.

What are we to understand by the phrase, 'first estate', and who are those angels that did not keep it?

Note:

Just so there's no speculation, I come from an LDS background.  My motivation for asking this question is to know how those outside of my faith understand by this verse, but answers consistent with LDS theology are also welcome.
The Strong's for this is:


  archē
  ar-khay'
  From G756; (properly abstract) a commencement, or (concrete) chief (in various applications of order, time, place or rank): - beginning, corner, (at the, the) first (estate), magistrate, power, principality, principle, rule.


Sounds like it means they gave up their rank or position, in addition to their "habitation" (residence) in exchange for some wicked thing they desired. Now, as a result, they are enjoying their 2nd estate--in chains.