Korean Names question

It's been some time now since I re-started watching Korean dramas, and I've watch lots this year. However, I still can't get used to their first name...naming system.

Anyways, my quick question is, what is the korean name that is equivalent to "John"? 

As you all know John is a very common name around the world, with different localized versions of course (i.e. Juan, Yahya, Yohan, etc)

Do you mean equivalent as the most common name, or the one that means the same as John, or the one that sounds like John?  I think the most pertinent question is why do foreign names have English equivalents?  Do they really? Is it a construct?  Is it a name Koreans living overseas have decided is easy for English speakers to understand?  if so why?  Why do English speaking people have to be accommodated?  Why does no one ask what is the Korean name equivalent to the Slovakian name Ján?

As an English speaking person, I completely support the question of why English speaking persons have to be accommodated.  As a language English usually incorporates words and names of other languages.  As to the original question of what is the Korean equivalent to the English name John - please remember that John is the English translation of that name as it is written in other languages such as Spanish - Juan, Greek - Ioannes (there is no letter J in the Greek language) and other languages variations.   I am curious too as to why many cultures living in an English speaking country adopt another name for themselves instead of using their birth names.  Personally, I like and do try to pronounce the birth names of persons of other cultures other than English whenever possible.  (When naming my children with their English names, I researched before their births the meaning of their names beforehand.)

My question would be - is there always more than one meaning to the birth names of Koreans?  I noticed in many dramas how one person would question and sometime make fun of a person's birth name, sometime commenting that it can have various meanings.

 Booktiful Days:

A Korean birth name has only one meaning, but for knowing it, you need to know the hanja the parents chose. If you know the hangeul only, you can just speculate since each part of the name can have different meanings.

Thanks for the explanation.