Who coined it and where? And when? Steven Greenhouse wrote about the term in 1998 in a New York Times story about Microsoft office slang.

http://amafubme.blogspot.com/2009/08/open-kimono-jason-perlow-open-kimono.html

 Open the kimono -- A marvelous phrase of non-Microsoft origin, probably stemming from the rash of Japanese acquisitions of American enterprises in the 80's, that has been adopted into the Microspeak marketing lexicon. Basically a somewhat sexist synonym for ''open the books,'' it means to reveal the inner workings of a project or company to a prospective new partner.

And there is a Dilbert cartoon that features Dogbert as a consultant who is explaining things to the pointy-haired manager.

"Incentivize the resources to grow their bandwidth to your end-state vision. Don't open the kimono until you ping the change agent for a brain dump and drill down to your core competencies."

Urbandictionary.com defines it this way:

(adj.) - A business marketing plan that allows consumers to know what's behind the entire operation, with no secrets kept inside the proverbial kimono

Example:
"The new e-reader runs on an open kimono strategy, and sales are going through the roof."

and this recent headline

Reuters Opens its Kimono

Wire service makes reporting handbook freely available online

By Craig Silverman

and this --

I  have heard the term "open kimono" frequently used in business conversations. It means being totally open and honest with our customer. Hiding nothing. I am curious about the etymology of this term.

One story I have heard is the term dates back to feudal Japanese times. Warriors or adversaries would open their kimonos as a gesture of trust to show they had no hidden weapons. By this definition the term describes establishing trust in a business relationship. However, I have also heard the term goes back to WWII times and refers to the geishas or prostitutes opening up their kimonos to reveal what they were selling. By this definition the term is sexist and offensive and should be avoided.

Does anybody know where this term came from? Is it sexist? Is it appropriate to use, or is it offensive though generally accepted? Thanks for the help. I’m looking forward to hearing from you. -- BD

AND

Here’s the story as a Japanese lecturer has pieced it together. I can’t do better than quote from her e-mail:

...
As for the origins of the phrase, what I think it comes from is ''kamishimo o nugu'' - this came up in a Google Search as a chapter title translated as ‘Open Kimono’.

 Kamishimo ‘consisted of a two-piece costume worn over a kimono. This is probably the most well known samurai dress. The upper piece was called the kataginu, and was essentially a sleeveless jacket or vest with exaggerated shoulders. Alternatively, a long sleeved coat, the haori, could be worn, especially when traveling or in bad weather. The lower piece was the hakama: wide, flowing trousers somewhat like those found in the older hitatare’ See websites below (quote above is from first one).
http://www.samurai-archives.com/clothing.html
http://www.concentric.net/~Budokai/store/kamishimo.htm

The kamishimo would be removed inside the house and in informal situations.
My Japanese colleague says kamishimo o nugu means to relax, speak and behave openly. Nothing to do with showing you don’t have any weapons. So it seems someone has jumped to this conclusion, assuming it’s like a handshake showing you don’t have a knife in your hand.

As for the other possible explanation, no, don’t think so. But here’s something on kimono, geisha and prostitutes:
http://www.2wice.org/issues/uniform/kimo.html
The key point being that the sash is tied in front, not behind as it normally would be.