To begin with, it is a matter of scholarly consensus among Classicists and philosophers that the concept of “Will” was absent from Greek thought and that St. Augustine was the first to develop it. Aristotle, for instance, had the notion of practical cognition and not ‘will’. “Akrasia” can only be loosely translated as “weakness of the will” simply because we do not quite know how to translate it otherwise.
X says: Isn’t that basically a faculty of volition, something that is the first thing one learns to express in any language?
In so far as this sentence is about psychology, you do not have a clue either about its history or where it is today. In the Middle Ages in Europe, one spoke about a “faculty of Volition” as a part of human psychological makeup. Today, no psychologist (from any research programme) speaks in terms of “faculty psychology”.