The date of Arador's birth appears only in The History of Middle-earth volume XII, The Peoples of Middle-earth. It cannot therefore be considered completely reliable.
As for all the later Kings of Arthedain and Chieftains of the Dúnedain, the 'Ar(a)-' element of Arador's name means 'royal' or 'kingly', and relates to their descent from Isildur. The '-dor' part of his name, however, is problematic: it might relate to the common (n)dor 'land', or it might be a variation of taur, in the sense of a royal or noble title. Since it is known that not all of Aragorn's descendants had interpretable names, it is also perfectly possible that the second part of Arador's name actually means nothing at all.