chitties is puttingtitties and chechies together. Somehow it sounds asfunny to hear as to say in place of either chechie or titties. Those all can be used for small boobies.
"She's got some big tits! But she's chubby, so.. Chitties."
"Hate it when you can't tell if she's fat judging from a pic. She could have some nice titties, or they could just be some chitties. And they probably have some big ass nips too."