Xannies is a slang term for Xanax, an anti-anxiety medication often abused by satan worshiping skateboarders.
"I slipped myself some pink Xannies
And danced around the house in all-over print panties
My mom's gone, that fucking broad will never understand me
I'm not gay, I just wanna boogie to some Marvin"
-Tyler the Creator (yonkers)