A first principle is a basic, foundational proposition or assumption that cannot be deduced from any other proposition or assumption.

In mathematics, first principles are referred to as axioms or postulates.

In physics and other sciences, theoretical work is said to be from first principles, or ab initio, if it starts directly at the level of established science and does not make assumptions such as empirical model and fitting parameters.

Aristotle calls it "the first basis from which a thing is known".  A foundation holds a house, a map leads a plane, an anchor holds a ship at harbour etc...the foundational truths will make you not err from the Way.

If I don't understand righteousness, then I am still a babe and hence do not understand the first principles of God

What is the doctrine of righteousness? Listen to teaching today on being “pierced by the revelation of righteousness”