In my mind it will always and forever be the CD-ROM drive, but any drive added to a standard Windows system (including partitions) will just continue the alphabet from C. So if you install a second hard drive (or partition your only one) it will become D, the next one will be E, and so on:

I’ll leave it to someone else to convey this in a biblical fashion.

Fabled? It's perfectly ordinary. I see the D drive all the time. At home it used to be an HDD to store things that didn't need the speed of the SSD (media, documents, etc), and now it's where USB drives end up on my work laptop.

D: for opdtical drive.

There were times when a Windows reinstall would name the system drive E: instead of C:, usually if one tried to reinstall without reformatting. That was truly, horribly cursed.