The great Les Dawson specialised in this genre of the British comic tradition. Looking from the 21st century, surely we are just talking simple sexism. No, we are not.
My grandmother lived in a simple two-up two-down terraced house in working class London; she grew up in one very similar, just around the corner. She was the eldest of fifteen children, when my mum was growing up either side of the Second World War, they all lived within walking range of each other, and of nan: the mother, or mother-in-law.
The houses were laid out like this:
Downstairs were two rooms. The front room, literally the front room, was the holy of holies: in there was the good China, the good furniture, and it was only used on special occasions or when someone important (for which read posh) came round. Day-to-day, the living room (sometimes, if there was no kitchen lean to at the back, the kitchen too) was the room that was heated and, so, lived in. For working class families less comfortable than mine were, even less space had to suffice.
The man of the house worked; his wife was at home, though she commonly took in work (my nan also ran a market stall on the Sunday market in Petticoat Lane after she was widowed at just 44). Kids, if possible, played out in the street ( there was no traffic to speak of). The women of the family were forever in and out of my nan’s house. In traditional working-class households the home was a female dominated zone, which men came and went from. And if family were in and out, the dominant woman in the family was very dominant. With my grandmother’s mother dead, that was my nan; for most husbands, it was the mother-in-law.
Hence, the mother-in-law as the bogey woman of traditional working class humour. The woman whose so close relationship loomed over the female dominated space the man could not control.
And Les Dawson? Les Dawson was one of the great British comics, steeped in the tradition of British music hall comedy. Back in the ‘seventies, a big TV hit was The Good Old Days, a direct homage to music hall filmed in the wonderful surroundings of the City Varieties.