The phrase "keep buttoned up" means to keep something private or confidential. Some synonyms for this phrase include "keep under wraps," "keep secret," "keep hush-hush," and "keep quiet." These phrases all convey the idea of keeping information hidden from others. Other similar phrases include "tight-lipped," "close-mouthed," and "clam up," which imply a reluctance or refusal to share information. It's important to be able to recognize these synonyms as they can be useful in a variety of settings, from professional to personal. Knowing when it's appropriate to "keep buttoned up" can help avoid misunderstandings and maintain trust in relationships.