Is 'Pig's Head Madness' a folk term for mumps? What is the origin of this colloquialism?

Yes, "猪头疯" (zhūtóufēng) is indeed a very vivid colloquial term for mumps in folk language.

The origin of this name is actually quite easy to understand if we break it down into two parts:

1. "猪头" (Pig's Head)

This part is very straightforward.

When one contracts mumps, the most typical symptom is inflammation and swelling of the parotid glands, located below the ears and beside the cheeks. Sometimes only one side swells, sometimes both.

Once the cheeks swell, the entire face appears round and large, and the contours of the face and neck become indistinct. From an appearance perspective, this resembles a pig's head. In the past, people liked to use common things around them as analogies to describe phenomena. They felt this disease made people's faces swell like a "pig's head," and thus this term spread.

2. "疯" (Madness/Wild)

This character "疯" (fēng) does not mean that a person will become mentally deranged or go mad.

In many local colloquialisms, the character "疯" is used to describe a state that is fierce, develops rapidly, and is uncontrollable. For example, when we often say a certain plant is "疯长" (fēngzhǎng), it means it grows exceptionally fast and luxuriantly.

Mumps, as an acute infectious disease caused by a virus, has the following characteristics:

• Rapid onset: One might be fine today, but start having a fever and jaw pain tomorrow.
• Highly contagious: Easily spreads rapidly among children and adolescents.
• Obvious symptoms: The swelling process is also relatively rapid and severe.

This characteristic of the disease – "coming quickly with fierce momentum" – was vividly described in folk language with the character "疯" to convey its severity.

Therefore, putting these two parts together, the colloquial term "猪头疯" vividly depicts the typical characteristics of mumps: a disease that can make the face swell like a pig's head, and has a very fierce onset.

This is a very down-to-earth, life-like term. Although it may not sound very elegant, it truly encapsulates the most prominent external features and the state of onset of this disease, making it immediately clear what is being referred to.