I don't think the "meaning" given here completely captures the origin of King as a given name.The explanation would be accurate for the origin of King as a surname back in medieval England. However, the modern use of King as a given name is either a transfer from that surname (particularly in honor of Martin Luther King, Jr.) or a use of the modern word "King" as a name, just as "Princess" and "Queen" have been used as names for girls as direct uses of the modern vocabulary words. [noted -ed]
The explanation would be accurate for the origin of King as a surname back in medieval England. However, the modern use of King as a given name is either a transfer from that surname (particularly in honor of Martin Luther King, Jr.) or a use of the modern word "King" as a name, just as "Princess" and "Queen" have been used as names for girls as direct uses of the modern vocabulary words. [noted -ed]