Just finished a fun little book: The History of Underclothes, by C. Willett and Phillis Cunnington. This 266-page Dover reprint, first published in 1951, is a scholarly review of both mens’ and women’s underclothes from ancient times to the 1930s. Like you, most likely, to me the subject is most interesting. My beak was piqued about ten years ago when this photo appeared in our local paper:

The story was that these were the set of roomy bloomers that once belonged to Queen Victoria…. the drawers have a 56-inch waist. They have been added to Britain’s Royal Ceremonial Dress Collection at Kensington Palace…. if you care to go see them in person.

The authors outline the five functions of underclothes:  (1) to protect the body from cold;  (2) to support the shape of the costume (think: bustle); (3) for cleanliness;  (4) as erotic stimulation; (5) as a matter of class distinction.  Can’t say I read it word-for-word but it was a fun browse.