@merrymouse
Maybe this Catherine Tate character is similar to the 'Karen' caricature in the US?
Perhaps part of the issue is that our perceptions of class and its influence are very different in the UK. Maybe if 'Karen' was called something different and was shouting at a shop assistant to hurry up because her 4 wheel drive was parked on a double yellow and she need to get her children to Mandarin classes we would 'get it'?
However, for me, 'Karen' is a harassed nurse of 52 living in Ayrshire, and I want her to be able to speak to the manager, because her concerns are usually ignored.
Yeah, I think in terms of its origins, the person it is describing is closest to a sort of soccer mom, but the emphasis is more on how the individual treats people like retail workers. So someone with a certain amount of monetary power in terms of consumer shopping, so probably not too young, with a family, very middle class, who is entitled with regard to how they treat low-paid employees in places like the grocery store or M&S.
Somehow it came to be applied to any women of that age and class who had a certain look, or whho the speaker thought was a bit of an old fogey.
While the original characterisation wasn't particularly nice I think it's probably true that a lot of people recognise the type of person it was referring to, and it's easy to imagine some foot-sore harassed worker at the supermarket thinking it about customer. Whereas the way it is used now, 99% of the time it doesn't even make any sense and you don't really know what they are trying to say.
Left to itself it would probably die out quickly because its no longer a useful shorthand for anyone.
Somehow it widened out