that does not assume the CONCEPT underlying the word was not understood by Christians
Your JWesque proof-texting notwithstanding there is no description of anything approaching the concept of a trinity anywhere in Paul's writings.
Are you really asserting that the earliest illiterate Hebrew christians described their god in esoteric Greek terms like homoousios?
No ordinary christians today even begin to understand the nuances of person, essence and substance. Almost without exception they worship a committee of three gods or a single god with three hats. Already in this thread we have had every heresy offered by self-proclaimed christians.
It is evident you cannot explain it in simple terms. No christian who believes in the trinity should have the cheek to criticise the cult's "overlapping generation".