Why are school swimsuits with name tags such a popular item in otaku subculture? How did it get so popular in otaku subculture?

What is the name of the proper name for name tag that's commonly found on female school swimwear? Sometimes it just says the name, sometimes just the class number, and other times both. What significance does it play both in-universe and in real life?
What is it called?

There doesn't seem to be a separate name for that kind of school swimsuit, but the the part with name and class written on it can be called either ゼッケン (zekken, literally meaning cloth) or 名札 (nafuda, literally meaning name tag).

Why is it popular?

I don't think there's a definitive or objective way to answer why school swimsuits are so popular in anime, but here are translations of some of the possibilities mentioned in various answers to a very similar Yahoo Chiebukuro question:


It's easier to draw everyone in school swimsuits than to make up a swimsuit design for each character
They make the character seem younger, inferior, and/or weaker
They expose some skin and show off a character's body while still seeming immature
It's moe (see related question: What does &#39;moe&#39; mean?)
They have a simple design which is appealing
Lolicons prefer school swimsuits, and it's easier to please all of lolicons with school swimsuits than to attempt to please all the other groups with widely varying preferences


What is its purpose?

From the Japanese Wikipedia article for gym uniforms, which typically also include the same patch with a student's name:


  In order to manage students and in the event of an accident while
  exercising, the student's name, class, attendance number (similar to
  an ID number), etc. are filled out on a white cloth name tag that is
  sewn or embroidered onto the clothing.


There was no relevant information in the article specifically for school swimsuits which is why I used the article for gym uniforms in general.