It is unknown what his name was before this. He is currently known as Telnan, but comments made to Vlad seem to indicate that this name was adopted after he began his training, inasmuch as Telnan seems to think that 'Telnan' might mean "student", or something similar.
It might be that Telnan is the reincarnation of Tazendra. He is of the same House, Dzur, he certainly appears to be young enough to have been born shortly after her death, and his cheerful personality has a certain resemblance to hers. Since Tazendra died fighting a Jenoine, and was given to Deathgate, it would certainly make sense that she would have been judged by the Gods as being worthy of being reincarnated expeditiously, and her reincarnation guided towards a Great Weapon. Additionally, a brief view of Telnan's history of violence explains that he had joined a private army hoping to see some fighting but that he ended up killing the other three members of his squad before accomplishing anything. This mirrors the experience of Tazendra in the book "The Phoenix Guard".
It may also be significant that Sethra thought that he was worthy, even at such a young age, of being trained as a Lavode, just as Tazendra was offered that training. It is also especially significant since Sethra pretty much states that no-one else in the Dragaeran Empire has been offered that training, although she also implies that his possession of Nightslayer has more than a little to do with her offer to provide said training.
Since possession of a Great Weapon gives an individual a connection to "something beyond this world", it is interesting to ponder what Fate may have in store for him.