Syntax: “But what it was I had forgotten”?

Question

I had heard some story of her too, a critical, unpleasant story, but what it was I had forgotten long ago.

This is a sentence from The Great Gatsby by F.Scott Fitzgerald. The clause after the but kind of confuses me--it looks not that familiar to me, the way it's written. It's the very first time to see structure like that. Is it for some literary effect? Like emphasis? It would be more familiar to me, if it were written as . . .

but I had forgotten what it was long ago

or

but it was what I had forgotten long ago

What might have been the reason for F.Scott Fitzgerald to write that way?

Answer 1

This is a simple matter of object/subject reversal, which is perfectly valid. You correct deduced that

• what it was I had forgotten long ago

Is equivalent to:

• I had forgotten long ago what it was

The sentence as quoted from the book is quaint, but not wrong.

I did the laundry. The laundry I did. I had forgotten to do the chores. The chores I had forgotten.

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As a matter of style, one might prefer a comma in the reversed form:

• I did the laundry; the chores, I had forgotten.

• . . . but what it was, I had forgotten.

But who am I to quibble with F. Scott Fitzgerald's style? He has sold a lot more books than I have!