There was also an alternative theory, that some part of ChatGPT's RLHF came from Nigera, where "delve" is used much more frequently in business English. An article I could find about the subject: https://www.theguardian.com/technology/2024/apr/16/techscape.... As you can see it's pretty light on facts and heavy on speculation, which is why I'm calling this an alternative theory.