I've never heard of it before. I looked it up on the Net and I found some references to the phrase in very old books but none of them made it clear what the meaning was.
If I had to guess, I'd say it meant something like there are many different ways to live or do things and none of them are better than any other. Perhaps it's a response when someone is believes strongly that something should be done a certain way but they should really be more tolerant of differences.
It might be common in places outside the UK so I'd like to see others' opinions.