From the NYT story: “I was on an airplane,” Birkin said, explaining the bag’s genesis, “when a plastic bag holding all my things broke and everything fell out — my date book, papers, everything. Just as I was saying how I wish Hermès would make a bag that could fit all my things, the man sitting next to me happened to work for Hermès — it was Jean-Louis Dumas, the head designer! They already had the Kelly bag, named after Grace Kelly, so he began work on the Birkin bag. I went down to the atelier, and he had made it in cardboard. And we talked about it, and I said they should make some changes, like making pockets bigger. And that’s how it was made.”
Just like that!