What is the meaning of “stews” in WLC 139?

Question 139 of the Westminster Larger Catechism reads:

What are the sins forbidden in the seventh commandment?

A. The sins forbidden in the seventh commandment, besides the neglect of the duties required, are, adultery, fornication, rape, incest, sodomy, and all unnatural lusts; all unclean imaginations, thoughts, purposes, and affections; all corrupt or filthy communications, or listening thereunto; wanton looks, impudent or light behavior, immodest apparel; prohibiting of lawful, and dispensing with unlawful marriages; allowing, tolerating, keeping of stews, and resorting to them; entangling vows of single life, undue delay of marriage; having more wives or husbands than one at the same time; unjust divorce, or desertion; idleness, gluttony, drunkenness, unchaste company; lascivious songs, books, pictures, dancings, stage plays; and all other provocations to, or acts of uncleanness, either in ourselves or others.

A little historical review will be helpful for explaining why this language would appear in a fifteenth century document like the WLC. Public bathhouses have a long history from the Indus Valley Civilization —> Greece —> Rome —> Ottoman Empire —> Japan —> to Indonesia, etc. According to Virginia Smith in Clean: A History of Personal Hygiene and Purity (Oxford University Press, 2008), "By the fifteenth-century, bath feasting in many town bathhouses seems to have been as common as going out to a restaurant was to become four centuries later."

The British learned a lot about bathhouses from the Romans. The plague caused a decline in bathhouses, however they still existed on the “other side of the tracks” and became synonymous with houses of prostitution. The word “bath” is derived from Latin balneum, and “brothel” from bagnio. A common medieval term for a brothel was "a stew." Public bathhouses, or stews, of that era developed this sort of reputation, and in our day we might compare them to massage parlors.

Note, the catechism states that not only is prostitution a sin ("resorting to them"), but even "allowing," "tolerating," or "keeping" them as if they should be approved for others is sin as well. Christians should do all they can to keep these things out of their communities.