They would have gotten away with it too if it wasn't, er, (checks notes) open source.
None. OpenTofu name comes from Terraform => TF => Tofu. Bao is another asian food, so it kinda fits (people involved with OpenTofu are not the same as people working on OpenBao, but why not have some common theme).
Bao (包子) is usually referencing a steamed bun, for those interested.
And is as tasty as the logo itself :)
So basically the cake containing the file to break out of the vault?
This one is already open though. The file is gone.