Another form of "the question"

[Jack Daw]

And this was the practice among most men in the western world, not just the kilted. With the possible exception of some very rich people, separate undergarments were introduced in the nineteenth century A.D. and became common only in the twentieth. I suspect that the main reason they became common at all was that the development of knitting machines made them economical.

It appears that the term "regimental" originated because some of H.M.'s regiments required the practice, at least among the O.R.'s, and the term "commando" (in this sense) was coined by people who were unaware of the regimental practice.
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YEP! The advent of the industrial revoluion in the 1840s resulted in the manufacture of a lot of new goods.