make a secret of something

• 不让某人知道某事；隐秘某事

make a secret of something的用法和样例：

例句

1. He has a keen eye for the secret of the thieves.
   他善于洞察小偷的隐秘。
2. If you do good, people will accuse you of selfish ulterior motives.
   你如果行善事，人们会说你必定是出于自私的隐秘动机。