As both travel lover and a history buff, I certainly knew what a portmanteau was – after all, fictional characters of yore would regularly be found packing such suitcases and hitting the unpaved, often muddy roads on the stagecoach or in private conveyances.
It wasn’t until recently, however, that I came across the term’s more interesting usage while reading a current novel. One of the characters, a writer, referred to portmanteaus and I knew he didn’t mean travelling bags with two compartments. After a rendezvous with a trusty dictionary, I emerged, minutes later, enlightened. There are, indeed, two parts to the other portmanteaus, which are words formed by combining two different terms to create a new entity, blending their sounds and meanings.
We’ve all used portmanteaus without realizing it: smog, for example, is a combination of smoke and fog. Or consider brunch, which combines breakfast and lunch. One of the most current examples is that of the podcast, an addiction for the cellphone generation who listens on the go; it meshes iPod, a term for the listening device, with broadcast, the descriptor of the content.
Lewis Carroll, author of the renowned 19th-century novel, Through the Looking Glass: Alice’s Adventures in Wonderland, was the first to use the term portmanteau for a blended word that contains some of the meaning of both of its parts. 
When Alice asks Humpty-Dumpty about the meaning of the word, slithy, from Carroll’s nonsense poem, “Jabberwocky,” the clever egg replies, “Well, ‘slithy’ means ‘lithe and slimy.’ ‘Lithe’ is the same as ‘active.’ You see it’s like a portmanteau—there are two meanings packed up into one word.” (https://www.britannica.com/topic/portmanteau-word)
The technical term for portmanteaus is blended words – not quite as picturesque or descriptive as the words themselves. They are a form of shorthand and, while they may sound odd to the unprepared ear, many are adopted into our everyday language and are so common that we don’t usually think of their origins.
Here are a few that have undoubtedly come your way and a link to some others; do share your own favourites!
Bollywood: The movie industry in India, a combination of Bombay and Hollywood
Bromance: A close relationship between two men, combining brother and romance
Chillax: Be calm, a combination of chill and relax
Chunnel: the tunnel between England and France that crosses the English Channel
Glamping: Luxury camping, a combination of glamour and camping
Mansplaining: Explaining something to a woman in a condescending fashion; combines man and explaining
Motel: An overnight way station for car/bus travellers, combining motor and hotel
Workaholic: Someone who works excessive hours, combining work and alcoholic
supergrammarian 