Oy veh! I'm singing with a retired policeman tonight - I'll have to be careful what I say with that knowledge added to my "useful knowledge" LOL

I've been reading the French side of Celine's blog in order to learn French beyond that taught to me in school in 1984. But in order to read the comments, you have to come to the English side, because no one ever comments in French. Therefore, I'm now going to attempt to translate my comments into French.

Your suggestion that Rozzer is derived from Chazzer is almost certainly wrong. The use of the word 'pig' to describe police dates from mid 60's liberal USA, and was quite unheard of in London before then. So your explanation relies on a strictly modern phenomenon to explain and old word. Also London idiom would not transmute 'hazzer' into 'rozzer', the shift is not what Londoners would do.

Rozzer is linked with another slang term of the time 'rooscher', now defunct. I did once read a reference, which maddeningly I cannot now find, suggested the following origin. Rozzer dates from c. 1870 when Sir Robert Peel set up the original London Police force, based in part on the Venice Watch, run at the time by Count Rosseretario or some such. I do not have the exact name. London idiom would easily trunsmute that to rozzer. It is also exactly the sort of thing that Londeoners do with language. Further evidence for this is that until recently the word was almost unknown outside London.

The only certain statement is that the etymology is lost.

Emrys Jones made the compelling point that London idiom would not transmute 'hazzer' into 'rozzer', but that 'Rosseretario' (the name of the Count in Venice upon whom Robert Peel modeled the Police Force) would have easily become transmuted.

In support of this, it is worth noting the related London slang word "Peeler", which is derived in an identical manner from Robert Peel's name.