Question Author
Well! What a can of worms I seem to have kicked over! But thank you both for educating this old fool in the ways of the modern world.
Much more prosaically, in my youth, between the wars, miffy meant milk in first! In "polite" drawing rooms it was considered bad form, when pouring tea, to put the milk in first "Rather miffy". And the saying extended to criticism of any breach of good manners.
After all that, my question was simply - why was this thought to be important?