On 6th August 2008, Disney announced that they will replace Toon Disney in the United States and Jetix channels elsewhere in the world to the brand new Disney XD brand. Disney XD was to become a channel to focus on the male child demographic with live action series and also a home for new TV animation productions by Disney.
It was never really explained what the "XD" in Disney XD meant, one theory is that it was a recycled brand name from Disney's former Xtreme Digital, which was an online network on Disney.com that showcased exclusive Disney content such as videos and music, with the XD in the name of the Disney XD TV channel meaning "Xtreme Digital", however this is not true. Another theory is that it's a laughing face emoji.
According to Effectv, the advertising sales division of Comcast Cable which runs ads on Disney XD for Comcast customers in the United States, the XD is actually a laughing face emoji.
From the description on Effectv's website:
Disney XD is embodies the spirit of self discovery and accomplishment. The winning goal, the victory lap, the high five, a kid’s life is all about accomplishing things and finding out what they can do, and Disney XD is a window into that world. It’s an entertainment brand where kids have fun challenging themselves and discovering their strengths. With characters, action and stories that inspire kids to always give it their best, Turns out our network name means ‘big laugh’ in texting shorthand. It’s an Emoji, which is Japanese and very complicated. Let’s just say if you take ’XD’ and rotate it a quarter turn to the right, you get a wide smile with squinting eyes. You could say that’s how we roll: we like to start with a laugh then turn it on its ear.