The "Dictionary of Chinese Character Forms and Meanings" (Sichuan Dictionary Publishing House) explains: Because "center" means the end, it is extended to "end".
It is indeed difficult to understand from "center" to "end". The "Dictionary of Interpretation of Chinese Character Forms and Meanings" believes that "please" is also derived from "center", which is equally difficult to understand.
I also checked four oracle-bone inscriptions books, but no further evidence was found.
Let’s make a non-authoritative guess: Oracles of the Yin and Shang Dynasties once recorded some combat operations of hunting and surrounding enemies (this is a fact). When animals and enemies are in the center of the encirclement, there is no way out. . The "center" is the "end" for the besieged, and the enemy will therefore "beg" not to kill. "Oracle Bone Inscriptions" has an explanation for the shape of "Yang", which believes that the objects on the human body are shackles. It seems that "Yang" has some connection with the captives.
Of course, what I mentioned above about "combat" and "enemy" is not accurate enough. When slave societies arrest people, they often capture civilians from other countries as slaves. But no matter what, there were roundups, and sometimes the king himself led his men to arrest them.