She is the cat's mother - origin

[barmy]

What is the origin of the above phrase and why did come into use as a rebuke regarding being polite?

I know it fis airly old as grand mother used to say it but I never did understand the origin.

Thanks

[Quizmonster]

I'd guess it came from too far back in time to establish an actual original usage. The meaning, though, as you suggest, is that when someone - usually an adult speaking to a child - says, "Who's �she', the cat's mother?", it is an indication that the adult feels the child is being disrespectful.
Instead the child should have said 'Your friend' or 'Auntie Edna' or whatever else would have fitted the situation rather than just the unspecific word 'she'. In other words, one might call a cat or its mother 'she' but one shouldn't call one's elders and betters by that dismissive name.

[Quizmonster]

Click here for some confirmation, though there is more specific gen about its age.