It is surely a tradition handed down from early Jews experience of John the Baptizer.Where did that thinking originate? Is it necessary? Is it a decree of God?
It seems definitely a Christian interpretation of the idea of infant circumcision and becoming old enough (in the Catholic tradition) to formally and publically assert one's faith at comfirmation.
Every culture and societies have their ways of preparing adolescents into young adulthood by certain rituals.
I was gathered into the worship patterns and faith from my own first family. As I got older and was attending high school the ritual for us young folks was what we called "dragging Main"--riding up and down the main avenue and evaluating the girls and guys who were driving by in the opposite direction.
Later, I was able to still connect with my Christian upbringing and now I am posting on this site, trying to "set people up on blind dates" with Jesus!