But a lot of those do make sense.
No pot to piss in - too poor to afford a chamberpot
low man on totem pole - figures on a totem pole are necessarily arranged vertically, as are people in a heirarchy
and if you think witches tits are warm, you've never been to bed with an actual witch
on the other hand, you can eat your cake and have it too: when you eat it, you still have it, it's right there in your stomach.
barfo