often seen in the street without a hat

I think I always assumed cans were buttocks, when I bothered to think about it at all, which would obviously be in the same gaze-range as legs. But I feel like cans being breasts is vaguely familiar too. And gams are definitely legs. I want to know where 'tits' comes from now, is it a genuine reference to birds?

I hope you don't have cholera and your curfew situation is okay, you're in South Sudan omg!