Where did DirectX code names come from?

I worked for a company where they started development on a project with a code name. At this company the engineers always used code names and never product names even after a product was released. It was rough working in support always translating for everyone when you existed between both worlds.

Then on this project they CHANGED CODE NAMES midway through development. The confusion was needless and we burned so many cycles clarifying things.

I saw Manhattan, Orange and Kool-Aid, and assumed the others were also the names of drinks. Nope!

Apple has code names for code names.