Ever since I was a kid I have wondered why we say "he is a friend of
mine" instead of "he is a friend of me". Steven
Pinker would love that! Why indeed do we use mine in what
instinctively [We will soon be reviewing Pinker's book called The Language Instinct
- M&M] feels like a weird
construction? The book is mine, the friend is mine, but the friend
is a friend of ME. (Don't worry, I am not suggesting that we change this
usage; I am simply pointing out that it is somewhat unusual.) Note
that usage guru Fowler doesn't even mention the possibility of a
construction like "friend of mine"! He does, however, note
that mine was originally equivalent to my and was only used
before nouns beginning with a vowel or an h. Eventually my
came to be used in all such instances and mine became a pronoun.
Note that the Encarta
Dictionary recognizes the "friend of mine" usage.