D♭♭

Introduction
In music, there are a couple rare marks known as "Double flat" and "Double sharp". While a sharp or a flat raises or lowers the pitch half a tone, respectively, double flats and double sharps raise or lower the pitch one full tone. Since D is one full tone above C, D double flat IS C. Therefore, the language D♭♭ IS C as well.

Pronunciation
D♭♭ is pronounced "Dee double flat"