To keep something under wraps

Origin

The phrase draws its meaning from the literal act of covering an object to protect it or conceal its identity. Imagine new merchandise in a store kept carefully hidden under protective cloths or paper, or a gift meticulously wrapped to prevent its contents from being seen before the big reveal. This physical act of concealment, common in various aspects of life, began to be used metaphorically in the early 20th century to describe the act of guarding information or plans. The vivid image of something physically covered and unseen became the perfect shorthand for holding back a secret until the appropriate moment for its grand unveiling.