I think this is highly amusing.
First, the background: Plica polonica (Polish plait) was a strange hair disease that was common well into the 19th, and even the 20th century. Basically, it involved the tangling, "felting" of long, dirty hair, but it was much more than dreadlocks - the hairs themselves became engorged and filled with a kind of liquid or pus. According to medical descriptions, it emitted a foul odor. Doctors were divided as to whether it was a condition caused by poor hygiene, or something else, such as drinking foul water. As the name it was known by, "Polish plait," indicates, it was far more common in eastern Europe. Since hygiene was so poor all over Europe, that it was so common in Poland would have seemed to indicate that there was something unique about Polish conditions - and it wasn't poor hygiene alone - that caused it. It was also observed to grow in animals in Poland, but not elsewhere.
In addition, there were superstitions attached to this condition. The people believed that a Plica was a supernatural phenomenon and the growth of one did not indicate a health problem, but on the contrary - it indicated the relief of a health problem. Growing one was lucky, it meant you had an illness but were getting better. The people who grew them did not want to cut them off, and since it was seen as having magical properties, people rubbed things into their hair - honey, dirt, etc. - to try to induce the formation of one. Although it became closely associated with Poland (and discussions of the Plica make appearances in rabbinic literature), and it could obviously be found wherever hygiene was lacking, there are apparent references to it even in Shakespeare, where it is called an elflock. In one issue of the Philosophical Transactions from 1746, there is an article about an English country woman born in 1645, and her Plica polonica, which she had grown beginning at age 14. So despite the stereotype, it could be found all over Europe.
Thus, the background. In 1650 a clergyman named John Trapp published a commentary on the Book of Proverbs.
Commenting on the verse in chapter 7, verse 10, "And, behold, there met him a woman with the attire of a harlot, and wily of heart." Trapp gives the following comment and mini-sermon:
Trapp means to explain the Hebrew for "attire of a harlot, the "שִׁית זוֹנָה." He explains that this is a kind of tightly fitted, plaited garment. He then cites the Latin of Lavater, referring to something plaited, which he glosses are pleated garments or plaited hair. This is "the attire of a harlot." But since in Latin "plaited" is "plica," since Lavater wrote "vestitus in quo plica," this reminds Trapp of the dreadful condition Plica polonica. This has nothing at all to do with the verse. But since he is talking about the attire of a harlot, a sinful way of dressing, since the word sounds the same, he cannot resist bringing this up:
"Let such take heed to the plica polonica; that dreadful disease."
This has nothing to do with anything, but it probably could strike revulsion and fear in the heart of the reader, just as Trapp intended.
I am reminded, and friends I showed this too are reminded, of various teachers who moralized in precisely this associative way. So here is John Trapp, teaching a verse in Proverbs, 350 years ago, the way I've been assured some teachers try to spread the value of tznius in contemporary schools.