Why are Python issues preceded by `bpo-`?

Question

I've raised two python issues, but can't work out why the issue numbers are referred to as bpo-xxxxxx where xxxxxx is the issue number.

What is the etymology for this, or what is bpo an acronym for?

Why is it generally written in lowercase?

Answer 1

The Python Developer's Guide's Issue Tracking page says:

The issue tracker is also commonly referred to as bugs.python.org and bpo.