A couple of months ago, the New York Times ran an article called “2023 Is the Year of the Long Walk.” The sub-heading began: “The 500-mile Camino de Santiago has inspired a host of new treks in places from Canada to Bhutan that let travelers take the slow route.” To my American ears, the word “treks” sounded off; I would have expected “hikes.” Same with the following sentences:
- “Here are seven new treks to keep in mind.”
- “In an effort to showcase this history, the Soca Region Foundation has turned the former front line into a 310-mile network of treks.”
- “Across the border in Georgia, Paul Stephens, who was volunteering with the U.S. Peace Corps, had begun envisioning a trekking route across the entire Caucasus range.”
Google Ngram Viewer reveals that “hiking” is about ten times more common in the U.S. than “trekking.” “Hike” and “hiking” are also used in the Times article, and to some extent the “trek”s are a case of elegant variation, or using a synonym to avoid word repetition. But Ngram Viewer also reveals that “trekking” is a Not One-off Britishism that has been gaining ground on these shores:
The OED reveals that the word derives from the Dutch trekken, meaning to pull, tow, or march, and was adopted by English speakers in South Africa in the late nineteenth century. This passage is from The Young Nimrods, 1882:
The OED reports that “trek” acquired the sense of arduous hike by 1911, and of an arduous hike one does for pleasure by 1955, when this quote appeared in The Times: “About 35,000 came last year, and more are expected this summer… They come to fish and shoot or to trek in the mountains. ‘Only the English like trekking,’ one agent said.” Unfortunately, the snippet doesn’t reveal the location being discussed.
Wes Davis credibly suggests that the American popularity of “trekking” may be correlated with the advent of trekking poles, which date from around 1990, and for some reason tend not to be called “hiking poles.” Just last month, the New York Times Wirecutter section ran an article called “The Best Trekking Poles” which used the term “trekking poles” nineteen times and “hiking poles” not once. No elegant variation for the Wirecutter.
notoneoffbritishisms.com 
As an old person born between 1911 and 1955, I relate to your statement, “The OED reports that ‘trek’ acquired the sense of arduous hike by 1911, and of an arduous hike one does for pleasure by 1955.” And to me, a “march” is an “arduous hike” taken by the military.
To me, as a Brit who likes walking, a trek is a multi-day walk in very inhospitable terrain taking all your supplies with you (so you don’t really trek in the UK, but the Appalachian Trail might count as a trek). A hike is often multi-day but at least a whole day. A bimble is up to couple of hours. A walk is any distance, but is the default word as we tend to prefer understatement (which is humble bragging in a way – casually dropping in things like “Oh yes I did the Camino, that was a pleasant walk that”). And the poles are walking poles or hiking poles.
You certainly can trek in the UK. Back in 2017 I trekked for five days across part of northern Scotland, seeing nobody and carrying everything with me.
I think the British also sometimes use trek to describe an unexpectedly long and disagreeable journey to get somewhere. For instance, I would sometimes say, “It was a real trek to get there”.
Of course the Americans have Star Trek …
As a northern English Brit, we use the word ‘trek’ in the negative to mean a long-winded journey. You’d say, it ‘were a right flamin’ trek up them ‘ills’ and the clear emphasis (to a fellow nE Brit, in fact most Brits) would be that the hills are not particularly ‘easy’ to navigate, that the journey is long, steep or made up of difficult, tiring terrain. You might also (if you’re being dramatic) use it thus: “I’m not trekking all the way to the bloody shops when I’ve just been!” Again, it’s used in the negative.
It is also of course used to mean the physical act of just trekking, though more among dedicated hikers and walkers. That hasn’t gone out of fashion, it’s just developed dual meanings.
I should qualify my previous statement to change ‘meaning’ with ’emphasis.’ The concept is broadly the same, but one you are using for the physical act with no emotion attached, and the other you’re clearly sending signals out that that journey is disagreeable to you. It’s just a subtle difference in usage, but it’s there in speech.
The “tiresome, awkward journey” sense might be conveyed by “schlep” in the US. I agree with a previous comment that trek suggests a longer journey than hike when used for an actual walk
Of course, schlep also could refer to conveying five grocery bags from your car to your house.
to this New Yorker, “schlep” conveys carrying rather than merely walking
No one has mentioned The Great Trek: https://en.wikipedia.org/wiki/Great_Trek – Also worth noting is the peak in the British use of ‘trekking’ on the Ngram, corresponding to the Second Boer War, 1899-1902: https://en.wikipedia.org/wiki/Second_Boer_War
By the by, I’ve heard Americans say ‘Sweet!’ which is a nice change from ‘Awesome!’ – But I thought ‘Sweet!’ was popularised here, starting in northwest England, around 30 to 40 years ago. Was it American all along?
I don’t have an answer to your question but I just want to say that I like the British equivalent to “sweet” or “awesome,” i.e., “brilliant!”
I overuse “brilliant!” – I hate myself a little more every time I say it, though it’s not the worst of my wordy sins. At least I don’t say “brill!”
Weirdly, since I’m someone who’s done quite a bit of organized hiking, I had not ever heard those hiking poles or walking sticks or whatever they are called “trekking” poles until I read this. Maybe my hikes did not qualify as “treks,” so my companions who used them were too modest to employ that term.
I grew up in Texas in the 50s and 60s, and to me, “trek” has always indicated something long and arduous; if it’s challenging but not draining, it’s still just a hike.
There’s also “pony trekking” in the UK, which is horse riding over a long distance (at least half a day, possibly several days) over tracks and trails in natural surroundings. Apparently this is called “trail riding” in the US.
Here’s an aquatic “trekking”: https://www.berkeleyside.org/2023/09/06/maya-merhige-swimmer-berkeley-high