open up one's kimono
open (up) one’s kimono
in. to reveal what one is planning. (From the computer industry, referring especially to the involvement of the Japanese in this field.) Even if Tom appears to open up his kimono on this deal, don’t put much stock in what he says.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.