Saying from York, UK meaning that a certain form of behaviour is
unacceptable - implication that it wouldn't be acceptable in
the village of Snaith, near York. The behaviour is so
unacceptable that, to personify it, never mind walking or running, it would be unable to even slither around Snaith before being challenged.
"That
gentleman has just disobeyed traffic laws and displayed a rude
gesture, informing me that I am a
masturbator. That wouldn't slither down in Snaith!"