Of zips and zippers

I have recently read George Orwell's 1984, and William Golding's Lord of the Flies, and was struck that both of them used the word "zipper". This surprised me, as I had always thought of it as an American word, and I wondered if I had an American edition.

She stood looking at him for an instant, then felt at the zipper of her overalls. 

1984

He laid a hand on the end of a zipper that extended down his chest.

Lord of the Flies

As always, though, it pays to be careful with assumptions. The OED has the first use of zipper in 1925, when it was registered as a trademark, with use of the term claimed from 1923. Only shortly afterwards (1928) it was being used in the Daily Express. 1984 was written in 1948, of course, and Lord of the Flies in 1954.

The first use of "zip" as a noun in the OED is also from 1925.

The nearest approach to sustained bitterness that he was ever to know was caused by the sight of the women on the Avenue with their galoshes fastened by the ‘Zip’— every last one of them.

E. O'Shaughnessy, Married Life

By an odd coincidence Eileen O'Shaughnessy was George Orwell's first wife. Subsequent uses are mainly British, including one from John Braine's Room at the Top from 1957. The Google ngram viewer results are as follows:

US English

Zipper takes an early lead, but is gradually overtaken by zip. I suspect this is largely because of other uses of "zip", ie as a verb, or to mean "nothing", etc

British English

Zip has a lead even before the introduction of zipper, and never looks back. However, the frequencies on this graph are less than half those in US English

It seems entirely reasonable, then, that Golding and Orwell would use zipper, although it reads strangely now.