Mentioned by
Kouzou Fuyutsuki in episode 26' as that possessed by
Angels. It is written in the book of Genesis in the "Old Testament" that at the center of
the Garden of Eden were the
"Tree of Wisdom" and the
"Tree of Life".
Humans disobeyed
God's command and ate of the "
Fruit of Wisdom", but what if they had eaten of the "
Fruit of Life" instead? Might this answer be the
Angels? Further, it is also told in
Genesis that they who eat of the fruit from the
Tree of Life shall have
immortal life.
Source: The End of Evangelion : Glossary contained within The End of Evangelion - Theatrical Program.