When/why did the "eternal light" begin in Jewish tradition?

Question

So Hannukah celebrates the miracle of the oil for the eternal light lasting eight days rather than one. But here's a question my nephew asked me that stumped me: why is the eternal light important in the first place?

Doubtless it represents the eternal and faith. But precisely when did it become a part of Jewish tradition and why?

Note: To be clear, I'm not asking about Haunnukah. I'm asking when the eternal light tradition began (since by definition, it obviously predates Hannukah).

Answer 1

You'll get a better answer than mine but here's what I remember. Some other nation came in and sacked their temple. It was defiled and pillaged. When the Jews captured it back, they went in and found only one oil lamp left. It should have been able to burn one whole day. It burned for eight days. Hence, the miracle of Hannuka.