In Terry Pratchett's Discworld series, "ladies of negotiable affection" are referred to as "Seamstresses", and are part of the "Seamstresses' Guild", despite not necessarily knowing how to mend clothes.
Pratchett's works often directly reference real historical events and phrases, so I was curious if this one was as well. The "L Space" Pratchett Wiki states in the article on the Seamstresses' Guild:
Also, during Seattle's earlier days, brothels were illegal, so prostitutes would list their jobs as "Seamstresses" when the cops came calling. During a period of minimal city revenues, it was required that Seattle prostitutes possess a "Seamstress license," and these fees became a major source of revenue for the city.
However, it doesn't cite any sources. I searched around the net, and came up with this Wikipedia article about Madame Lou Graham, which doesn't actually mention anything about "seamstresses", despite what this Scrapbook post says. This Seattle Met story on the history of prostitution doesn't mention anything about it.
Is this statement about Seattle prostitutes calling themselves "seamstresses" accurate? If not, are there historical cases of the term being used in this way?