I cannot trace out my childhood memory about 'Nachiketa'. (There are many unanswered questions from my childhood and student life are in queue.) But, as a teacher, when I have to 'teach' a unit on 'Nachiketa' in History; few questions raised in my mind : Why in this story a very young boy is shown to face the Death God? Why Nachiketa wants to know about the secret of fire? The knowledge about fire must be of good importance, otherwise why this simile?
Well, I used to see religious stories as a record of evolution process. It clearly shows life at that time. (Like, cow was scared and considered as a good property because at that time, life was agricultural oriented.) So, in this regard, I did not have any explanations about my questions about Nachiketa.
Last month, I read a very small book by Navjivan Trust, 'Asho Zarathrust ' and come to know why fire is god-like ans scared for Parsees (Zoroastrians). Before Zoro (not that fiction one.), people of Iran followed many gods. Zoro asked people to consider 'Fire' as a scared tool to reach the almighty. Well, why the fire? Because, someone has 'invented' it. Before that, fire was a scary thing, uncontrolled. But this 'invented' fire is very useful,controlled,and one can carry it with oneself (two stones at that time.). What a logical vision transformed as religious one !
Well, you got it ! Why Nachiketa wanted to know about fire. But, of course, as this story belong to the Hindu culture, there are many deep philosophical aspects which I do not intend to write here.
So is about the facing the death god. Hear is a child, who 'sees' the death. He is brilliant and aware and so fearless. He goes through the physical process of death at very young age and discovers what happens physically and psychologically when a human faces death. This is the answer I have on my own understanding, and with time it may change. I have not read 'Kathopnishd' where the dialog between Nachiketa and Yamraj(Death God) is given. But, I enjoy these answers.