To reveal what is being planned or to share important information freely. Similar to ”open the books” or an “open door policy,” opening the kimono means revealing the inner workings of a project or company to an outside party. Also referred to as “open (up) one’s kimono.”
The kimono is a Japanese traditional garment. There are conflicting entomologies for this phrase, but the one closest to its current business connotation is the idea of Japanese people loosening their kimonos to relax at home, much like loosening a tie. The term joined the business lexicon in the late 1980s during a period of increased global business interaction, most notably between Western and Japanese businesses.