Non native here: (without going to the link) here in South America we sometimes call a person by "Juanito" or "Fulano" they are some sort of "Jhon Doe" names and the insult being "you're so irrelevant to me that I don't want to learn your name" or "who is this random person that came uninvited" is not common but some people still use it from time to time. Is akin of calling someone "furniture" (yeah that used as an insult in Argentina mostly).
(going to the link) it make even less sense now....
Calling someone a Charlie.
https://greensdictofslang.com/entry/s7pwoia
Non native here: (without going to the link) here in South America we sometimes call a person by "Juanito" or "Fulano" they are some sort of "Jhon Doe" names and the insult being "you're so irrelevant to me that I don't want to learn your name" or "who is this random person that came uninvited" is not common but some people still use it from time to time. Is akin of calling someone "furniture" (yeah that used as an insult in Argentina mostly). (going to the link) it make even less sense now....