“Double is” is widely regarded as non-standard, meaning that it should be avoided in formal contexts. Still, since its usage is so widespread, it is worth examining how it came to be in the first place. How did this needless doubling of a word entrench itself so firmly into our spoken language?

As our regular readers will know, the relationship between our selected words is not always obvious. Even so, this month’s offering may appear particularly perplexing.

“Theo is a friend of Jane’s.” This phrase is unremarkable to most English speakers. However, on closer inspection, the sentence actually contains a somewhat unusual feature. It contains two possessive markers, the preposition of and the enclitic ’s, which might seem redundant or unnecessary. The double genitive has had English grammarians scratching their heads for centuries. How did it enter the language? What are its functions and uses? This article will answer these questions and shed some light on this peculiar feature of the English language.