keep under wraps
keep (something) under wraps
To keep something secret. Keep this under wraps for now, but Greg is definitely the one getting the promotion.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
keep something under wraps
Fig. to keep something concealed (until some future time). We kept the plan under wraps until after the election. The automobile company kept the new model under wraps until most of the old models had been sold.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.