Danny
I think Wiki have not told the full story. Snowdrops, as a nickname, was first known in the UK during WW2 when white helmeted US military police were seen everywhere. It was a US term.
In that time RAF police were known as SP's or Provosts.
Snowdrops is something which has transposed into our terminology in recent years and, like so many things, has been accepted as being the norm - it's revisionism.I suspect that the white topped caps weren't introduced until the late 40's or early 50's.I can't find any evidence that they were worn in WW2.Police armbands were worn and, possibly white webbing.If someone can provide photographic evidence to disprove me I'll be delighted to see it.
Sidetracking somewhat but a good example - "Butcher Bird" is another non contemporary name. Where did that come from?. It was always an FW or a 190 or a Focke-Wulf when it roamed the skies.