Ubuntu is a Nguni Bantu term meaning "humanity". It is often translated as "I am because we are", or "humanity towards others", or in Zulu "umuntu ngumuntu ngabantu" or in Xhosa, "umntu ngumntu ngabantu" but is often used in a more philosophical sense to mean "the belief in a universal bond of sharing that connects all humanity"

Taken from https://en.m.wikipedia.org/wiki/Ubuntu_philosophy

But yes, Ubuntu is based on Debian's Unstable branch.