vesuvius said:
Ian2 said:

In Britain, the nether region of ones posterior in the region commonly known as the buttocks is referred to as arse, across the pond however there are sayings like "your * is grass".


One could never image one saying "your arse is grass" in Received Pronounciation, but rather the Phonetic and more common version.

I think its a Potato Putarto thing  (interestingly 'Your Arse is Grarse' works phoeneticaly over here - though I've never heard anyone use that expression). 


Over here an * is a cross between a horse and a donkey.