I can tell you exactly how the term "pod" came to be what it is. It all started when ehell was on Delphooey, and they had the chat feature. One day some members were chatting online and someone mentioned that "pod" should replace the term "word" because it looked the same in type when reversed, or mirror image, or something like that. I wasn't in the chat room, I just remember reading how it came about.
It's just something that caught on.