Q: How do you explain the common construction seen in sentences like “It is a book of Bob’s” and “That is a stamp collection of Jane’s”?
A: We assume you’re referring to using both “of” and an apostrophe plus “s” to show possession.
This construction, often called a double possessive or a double genitive, is perfectly standard English. We wrote a brief blog item about it a few years ago, but it’s time for a more extensive update.
In the 18th century, some Latinists criticized this usage for not conforming with the grammar of their favorite language. The first one to look askance at it was Robert Lowth, the guy who gave us the myth that it’s wrong to end a sentence with a preposition.
But as the Merriam-Webster’s Dictionary of English Usage points out, the double possessive is “an idiomatic construction of long standing in English” and “a perfectly acceptable, perfectly normal form in modern English.”
In a construction like this, the preposition “of” is “followed by a noun in the genitive case or a possessive pronoun,” according to the Oxford English Dictionary.
Examples of this usage go back to the early 1200s, and would include phrases like the ones you mention as well as “a relative of hers” and “a customer of theirs.” There’s nothing wrong with any of them.
In fact, as the OED points out, possessive pronouns like “hers” and “theirs” are in effect double possessives already (at one time they were written “her’s” and “their’s”), and were formed “by association with the possessive case in such phrases as ‘a friend of John’s.’ ”
The New Fowler’s Modern English Usage notes that the double possessive also can be a very handy tool for sharpening an ambiguous possessive:
“In practice one of its most useful functions is that it enables English speakers to distinguish between the simple types a picture of the king (= an actual portrait of him) and a picture of the king’s (= one owned by him).”