#104 - Sept. 20, 2007, 12:12 a.m.
The term "sin'dorei" has indeed only recently come into popular use as the designation for blood elves. That is not, however, to say that the term has never been used before. On the contrary, like "quel'dorei", it was originally a Darnassian term.
"Sin'dorei" literally translates to "people of the blood" or "children of the bloodline", depending on context. Long before the War of the Ancients, night elf nobility frequently made strategic marriages in order to maximize the magical ability of their children. Over generations, the highest caste in particular set itself apart from the rest of the night elf people. These nobles took great pride in their lineage and therefore used "sin'dorei" occasionally and informally to refer to one another.
During Queen Azshara's reign, however, the arrogance and decadence of these high-ranking nobles reached new heights, and they began calling one another "quel'dorei", or "children of noble birth" (i.e., the Highborne). As a member of this caste, the queen approved of this new name and made it official. Later, after the Highborne were exiled from night elf society, they crossed the sea and continued calling themselves "quel'dorei". Other races tended to refer to them as "high elves". The elves still occasionally called one another "sin'dorei", too: they still took pride in their bloodlines, and "sin'dorei" hadn't lost its meaning any more than "quel'dorei" had. ;)
Keep in mind also that the song predates the War of the Ancients (over ten thousand years ago). Such songs aren't static: they change with the times. The elves have altered the song's lyrics a bit over the millennia to suit the situation. The intent behind the song has certainly changed as well. That is why the song's most recent incarnation so strongly evokes the recent Scourge invasion of Quel'Thalas.