There are plenty of words to describe the hot, hazy, and humid weather we've been enduring this August, but perhaps none capture the steamy, sticky, soupy conditions quite like the term "muggy." It's a funny word, if you think about it. That's something Rhode Island listener Alannah Farrell has been doing, and it piqued her curiosity. She asked:

During this hot, muggy summer, that term "muggy" keeps ringing in my ear. What on earth is that word, what is the origin of that word?
Alannah Farrell, Rhode Island

We love examining words here at the Curiosity Desk, and this is a fun one. As it turns out, the word “muggy," that staple term during the dog days of summer, comes to us from an unlikely source — those famed cold weather creatures: the Vikings.

"A lot of words have entered English through Scandinavian languages, particularly old Norse," said Ben Zimmer, linguist and language columnist for the Wall Street Journal.

"If you look at Scandinavian languages like Icelandic, and Swedish and Danish, you actually find a very similar word meaning mist or drizzle or something like that," he explained.

These words, including "mugg" and "mugga," appear to have made their way to England, where by the 18th century a written record of terms like "mug drizzle" and "muggy" began to emerge.

It is — of course — the humidity that makes weather muggy, so you can see how we landed where we did. And it's a particularly apt descriptor, when you consider the root of those Scandinavian words.

"All these words probably go back to the same Germanic root, which has something to do with slippery, slimy stuff," said Zimmer. "It's probably also the root of the word muck."

When I first saw Alannah's question, I figured the word “muggy” must somehow be related to the word "mug" — you know, the thing we drink coffee, tea or beer from. So, where does that version of the word "mug" come from? Well, the Vikings had homonyms just like we do.

"It probably also came from a Scandinavian source," said Zimmer. "But it’s just a complete coincidence that these two words just happened to be pronounced and spelled the same way."

Remarkably, this use of mug — for a drinking vessel — gave rise to nearly all other disparate meaning of the word today. That’s thanks to a curious trend in early 18th century England where, for a time, it was all the rage to fashion drinking mugs in the shape of exaggerated, grotesque human faces.

"And so because of those mugs with funny faces on them, that got transferred over for a slang term for a person’s face," said Zimmer.

Given that origin, you can see why calling a face a mug today still has a slightly negative tinge to it. A mug shot is a photograph taken of a criminal’s face. And mug, meaning face, often gets paired with the adjective “ugly.”

"From there you can turn the noun 'mug' into a verb meaning to make exaggerated facial expressions," said Zimmer.

That usage emerged from theatrical circles in the 19th century and is still with us. Today we might “mug” for the camera.

The other common use of mug as a verb, meaning to attack and rob someone in a public place, is also a reference to the face — and came not from the stage, but from the ring.

"We first start seeing the verb 'mug' being used in boxing around the early 18th century meaning ... to strike the face," said Zimmer. "And from there it got to be used more generally to beat someone up if you’re trying to rob them."

Those strange 19th century drinking mugs also inspired another slang use of the word in England, now out of fashion, meaning a foolish or gullible person. It’s this old-time usage that author J.K. Rowling said she had in mind when she introduced a new spin on the word in her Harry Potter series to refer to non-magic users: "Muggles."

"So, its just three little letters, and it has all these meaning and all these different histories," said Zimmer.

And while we mere muggles might not be able to wield a wand to any avail, we can at least occasionally step back and marvel at the magic of language.

Our thanks to Allanah Farrell for her question that led to today’s story. What’s yours? Email us at