Q From Stacey Newman, Australia; a related question came from Adrian Harris: Do you know the origin of bless your cotton socks?
A Short question, followed by inadequate answer. We don’t have much of an idea at all. But it may be worth putting down what is known.
Most writers turn, as I’m forced to do, to Eric Partridge. In his Dictionary of Catchphrases he records this expression in its older and longer form, bless your little cotton socks (which is the one I know and instinctively hunted for). He dates it from around 1905, presumably from personal knowledge since he quotes no examples. By implication he regards it as British. He says it was a middle-class way of elaborately thanking someone, which he said was extended a little later into bless your little heart and cotton socks.
My feeling is that it may actually be the other way round, Bless your little heart is recorded from the start of the nineteenth century. Though most of my sources for it are North American, the earliest ones are British — the first one I can find is in a slim volume of 1801, Farther Excursions of the Observant Pedestrian. It seems more likely that the cotton socks bit was tacked on as a fanciful or skittish elaboration, which then took on a life of its own.
It is hinted, or assumed, by other writers that the little cotton socks are those of an infant, so that bless his little cotton socks was once a pleasant-enough but meaningless — not to say slightly idiotic — term of approbation for a small child.