The onset of something bad. Its origins were a
combination of scouse wit & yorkshire genius. "To Go White" is a term often used in Northern realms when someone has smoked too much MaryJane. When this happened to someone we (the fools at the time in 1995) shouted whitesnake & sang "Here I Go Again on my own"
David Coverdale has therefore achieved a godlike status.
This then
developed into a saying for a bad thing, and now even my mum says it & shes a right tea-totaller!!!