Subjects like these have lost some popularity nowadays, but used to be very well read and written about in earlier times.
Under the heading of Scatology much literature exists about mainly pee and poo, and it was a popular and much more common subject to talk about than it is today.
One of the most famous representatives who was fond of this subject must be the Austrian-German composer W.A. Mozart, who used this in many of his letters to friends, family and loved ones and even in some compositions.
Very well known is his Canon, KV 559 for three singers, for which most likely Mozart himself made the naughty words. It is written using the Latin words “difficile lectu mihi mars et jonicu difficile”, but they mean nothing in their context. Mozart merely uses them to produce, when phonetically pronounced, an expression which sounds like someone saying in strong Bavarian accent “kiss my a**”. And if this were not enough for him, the following Latin word “jonicu”, when repeated multiple times, turns into “cujoni”, an Italian (contemporary spelling “coglioni”) word meaning “testicles, balls”. Combined this produced the sentence meaning “it is difficult to kiss my a** and lick my balls”. If you look it up on YouTube (search KV 559) it is very difficult not to laugh at the hilarious effect this produces when sung sanctimoniously.
Unfortunately for CF, mucus however has not shared the same popularity in literature, speech and music. Probably it was less interesting, did not smell and consisted mainly of colorless water – in other words it was much more boring than pee and poo. Nowadays it has seen a renaissance in the form of “Slime” which is used as children’s toy in various colors and settings.
Mucus however played a very important role in the teachings of Claudius Galenus, a famous physician in the Roman Empire (129-216) who developed the theory of the four humors, also called Humorism. In this, he put a lot of emphasis on the four bodily fluids blood, phlegm, yellow and black bile. He thought the balance between these in the body influenced a person’s character.
For the purpose of the subject of today – and for your consolement – it is good to know that according to this theory, having too much phlegm (mucus) resulted in the so called phlegmatic character, which resulted in dependability, kindness and affection. It was not until the 16th century that his theory was abandoned in favor of more “scientific” findings.
I hope this helps to put things in a broader perspective.