one-off and one-of-a-kind

Congratulations to Ben Yagoda on his new book Gobsmacked: The British Invasion of American English! If you like this blog, you are going to like that book. I was both gobsmacked and chuffed to see that I was among the dedicatees of the book (and in wonderful company). It even has an appendix of my UK-to-US Words of the Year! (And on that note—feel free to start nominating 2024's Transatlantic Words of the Year.)

Ben has been observing the transit of British English words, pronunciations and grammar for 13 years now at his blog Not One-Off Britishisms. So, to celebrate his book, let's look at one-off, the Britishism in his blog title.  One-off can be used as a noun or an adjective to refer to something happens once and won't happen again.

Ben's blog evaluates previously British-only expressions that seem to be catching on in American English, and one-off was one he first covered in 2011. In the book, he gives more historical context for both the British and American usage. Google Books charts (nicely redrawn by Eric Hansen in the book) provide a handy view of the trajectory of British words in American publications over time.

In the case of one-off, the first known occurrence of it is in 1930s Britain. It seems to take off in Britain in the 1960s, then shows up in the US in the 1990s, picking up speed as it goes along.  Here's the the relevant bit of the book:

 

He also categori{s/z}es each expression as to how entrenched it has become in AmE. In the case of one-off, it's "taking hold."  

While Yagoda keeps track of the migration of Britishisms, my (self-appointed) job on this blog is to give American English translations. One-of-a-kind seems a good candidate But is one-of-a-kind American English or General English? And is one-off displacing it at all?

My first stop is the Corpus of Global Web-Based English, whose data comes from 2012:

 

Now, we don't always hyphenate one of a kind (it depends on how it's being used in a sentence), but this chart at least gives a sense that one-of-a-kind is used proportionally less in BrE, since it has one-off to use instead. In the same corpus, unhyphenated one of a kind is still "more North American," but more gently so: 490 US hits to 320 GB ones. 

All of the Oxford English Dictionary quotations for one-of-a-kind are North American too—the first one from 1954 by American art critic Arthur C. Danto. (The first unhyphenated one is from 1977.) The OED does not, however, mark it as an American expression. 

Now, one-off and one-of-a-kind aren't exactly the same thing. One-off has a more temporal connotation: it's happened once (and won't again). That said, you could say, for example, that a person is a one-off or one of a kind meaning that they're a unique kind of person.

So is the existence of one-off hurting one-of-a-kind? It happens to be easier to look at the unhyphenated version in Google Ngrams and the hyphenated one in the Corpus of Historical American English, so let's look at both.

First, we can see that one of a kind has been increasing fairly steadily in both AmE and BrE, but it's definitely more American. One-off's appearance on the American scene has not caused one of a kind to become less frequent. 

And here's the hyphenated one-of-a-kind in comparison with one-off in American English since the 1940s. American use of one-off has taken off in the 21st century. One-of-a-kind is still used more, but the gap is closing:

How are both of these expressions doing so well?  Well, it seems to be because everything in the world has got(ten) more unique. Here's the Google Ngram for unique, going up-up-up in English generally since World War II. 

And just for the pedants, here's the chart for more unique:

(I wonder what proportion of the hits for more unique are just people complaining or warning against more unique.)

Anyhow, congratulations to Ben Yagoda on the success of his blog and the publication of his book! 
And so many thanks for this kind dedication: