Database prefix changed from wp_ to wpdp_

I considered posting this in Developing WordPress, but I think it wouldn’t be a very accurate fit.

So, I recently ported an extremely old test site I did to a new host environment, figuring I’d use it to practice with their tools. When I did so, a huge amount of work on the site stopped working, because the database changed prefixes– so what was once wp_usermeta became wpdp_usermeta. The update itself doesn’t really surprise me– I’d long suspected I should be using functions like update_user_meta() instead of fiddling with the database directly, from a best practices perspective. I’m more confused about how this change happened… to the extent of my knowledge, I didn’t update my version of WordPress or anything of the sort when I made the transition between hosts. If anyone has an explanation, I’d love to hear.