Thanks for this note...it is a very fundamental question, and one that is easy to answer.
Simply put, "Urantia" is the name of our earth – this planet on which we live. But what about the origins of the word itself? Etymologically speaking, the meaning of the word "Urantia" can be parsed as follows:
-ia = noun-forming suffix used for names < thematic vowel – i-+ L. noun suffix – a (first declension, nominative)
general: urania = heavenly (uran-) one (-ia)
specific: Urania = the heavenly one (Gr. Myth., the Muse of astronomy)
-tia = noun-forming suffix < – t-of L. past participle stem + – ia(cf., – tion and – ion)
U.B.: "-tia" is indicative of impersonal, while "-ia" is more personal
general: urantia = heavenly (uran-) place (-tia)
specific: Urantia = (y)our heavenly place (i.e., in the cosmos)
Here are a few passages about Urantia from The Urantia Book:
0:0.5 Your world, Urantia, is one of many similar inhabited planets which comprise the local universe ofNebadon. This universe, together with similar creations, makes up the superuniverse of Orvonton, from whose capital, Uversa, our commission hails. Orvonton is one of the seven evolutionary superuniverses of time and space which circle the never-beginning, never-ending creation of divine perfection—the central universe of Havona. At the heart of this eternal and central universe is the stationary Isle of Paradise, the geographic center of infinity and the dwelling place of the eternal God.
15:14.5 Your world is called Urantia, and it is number 606 in the planetary group, or system, of Satania. This system has at present 619 inhabited worlds, and more than two hundred additional planets are evolving favorably toward becoming inhabited worlds at some future time.
15:14.8 The grand universe number of your world, Urantia, is 5,342,482,337,666. That is the registry number on Uversa and on Paradise, your number in the catalogue of the inhabited worlds. I know the physical-sphere registry number, but it is of such an extraordinary size that it is of little practical significance to the mortal mind.
Your planet is a member of an enormous cosmos; you belong to a well-nigh infinite family of worlds, but your sphere is just as precisely administered and just as lovingly fostered as if it were the only inhabited world in all existence.
And please click to read our topical study titled "Urantia," where you'll read many interesting facts about this little blue planet we call home – the one that the celestials call "Urantia."