DWW: Kara, Josh, and the Meaning of "DC‪"‬ Dirty Work Wednesday

Kara has been dating Josh for a couple months, and just recently noticed that when she texted him something, her name came up on his phone as "D.C." But what exactly is the meaning behind her having those initials on his phone? Is it some sort of mistake? Or is it actually some kind of "secret reference code" that Josh has for her?