The etymology of the expression "Shuck your nan". Is based on the common London based insult "Suck your mum", "Shuck your nan" is rooted in the term "to Shuck an oyster" or to open/de-husk, meaning in order to fuck someones nan, she is so old she would need shucking - or prising open.
Which is nice.
"you're a plum mate"
"Yeah? Well Shuck your nan"
The wrinkly inner thigh of your Nan or grandma.
Your Nan's pork chops were shaking after I was done with her last night.
the best thing created since jesus. a lovely tall bin owned by somebodys nan.
person: you look like a clapped crab
me: you look like my nans bin
When you are so hairy like ya nans hairy puebes
Bro you are soo hairy
Like what?
Ya nans hairy puebes
The phrase you hear in public schools across Britain.
Boy 1: oi, suck ur mum
Boy 2: nah, suck ur nan bruv
Used as a way of garnering attention when the attention is on others.
Attention seeker: Your nan's tits