In our most recent installment, Webb’s Weird Words took another sidestep into etymology — to examine the building-blocks of medical terminology.

(Example: GASTR [stomach] plus ITIS [inflammation] = gastritis: literally, inflammation of the stomach!)

But did you know that less scientific terms like melancholy, sanguine and even humorous also have their origin in medicine?

They were actually bestowed on us by an ancient and now-discredited belief about emotional health; and to paraphrase the great Dave Barry: No, I am not making this up.

For about 2,000 years, it was thought that moods and feelings were governed by four bodily fluids — known at the time as “humors” (hum- once meant “moist,” as in humid). I know this theory — called “Humourism” — sounds like quackery; but keep in mind that dissection and autopsy were frowned on in the ancient world — so doctors knew considerably less about our internal system(s) than we do now.

To elaborate: The four liquids were blood, yellow bile, black bile and phlegm. And those in turn were supposedly produced by — respectively — the heart, liver, spleen and brain.

(If you’ll forgive a personal note: As I write this, I’m fighting off a sinus infection — so the brain-phlegm thing doesn’t actually sound that nuts to me just now.)

Those “humors,” in turn, were each associated with a certain emotion. Blood caused cheerfulness; yellow bile was associated with anger, black with sadness; and phlegm led to sluggishness (again, I can kinda relate at the moment).

If you had a proper balance of these liquids, you were literally good-humored. If they were out of whack — if say, you were overly cheerful all the time — this would make you eccentric, causing amusement and mockery. In other words: you’d be … humorous.

Yes, that is actually where we got those two italicized terms. In fact, the entire theory has now been so thoroughly dismissed that most people don’t even know it — though you will run into it in older writers like Shakespeare and Chaucer; and yet, despite its unfamiliarity, many terms we’ve inherited from this concept are still fairly common.

Phlegmatic, for example, means “calm, not easily excited”; pronounced fleg-MAT-ik, it is in fact derived from the supposed sluggishness of that yellow goop we all detest.

Bilious is a similarly extant term; pronounced BILL-yuss, it’s an adjective meaning “irritable, cranky” — an emotional state once allegedly caused by too much yellow bile. One of that word’s synonyms, choleric (KAHL-ur-ik), is likewise derived from humourism — since chol is a Greek base meaning “bile” (from which come cholesterol and cholera, among others). The second of these touchy-testy synonyms can be found in Shakespeare’s Taming of the Shrew (4.3), where Petruchio denies his hot-blooded wife a certain food because it’s “too choleric” — and will only make her bad moods worse.

The less-familiar splenetic is yet another “bad-tempered” synonym; it originally meant “sad” (i.e., too much spleen), but gradually morphed into an even nastier bad feeling.

Relatedly: Many readers will recognize the Greek base melan, meaning “dark” or “black”; it is found in such words as melanin, melanoma and yes, melancholy — which literally means “black bile” (i.e., sadness). In a special online note called “Humorless Words for the Bodily Humors,” Merriam-Webster also provides the rare but similarly derived synonym atrabilious.

By contrast, sang(r) is a Latin base meaning “blood” — present in such English terms as sanguinary (“bloody”), sangria (for its deep red color) and sang-froid (“courage, nerve, steadiness” — literally “cold blood”). Through humourism, the base also gives us sanguine, meaning “cheerful, optimistic” — that feeling formerly associated with blood.

And finally, humourism likewise provides the slang term lily-livered (i.e., “cowardly”) — the idea being that you’d feel unduly fearful if you didn’t have enough anger-producing bile in your liver.

In addition to Merriam-Webster, this column is indebted to the Online Etymology Dictionary and a terrific old text called English Words from Latin and Greek Elements. Perhaps it’s similarly indebted to the melancholy state of my own current health.

But I’m feeling fairly sanguine about that.