A Greek pun.
The Greek text can be read either as “born again” or “born from above”, i.e. from heaven. In the story, Jesus's interlocutor Nicodemus erroneously takes the first meaning and asks, with understandable confusion, how on Earth someone could crawl back inside his mother to be born a second time. Jesus then explains (sort of) by talking about being born of the spirit, providing context that makes it clear that he meant “from above” and that “born again” was a misinterpretation.
Thank you for sharing this insight, blessings!