Not a kid anymore spoken language
If someone is not a kid anymore, they no longer have the characteristics of a kid, which are innocence, naivety, irresponsibility, etc.
You can't deceive me. I'm not a kid anymore.
That hole is not large enough for you to crawl through, John! You are not a kid anymore!
You are not a kid anymore, so you should be responsible for your study.
The origin of this phrase is not clear.
The associates of public figures must not be suspected of being a part of any impropriety.
After being fired due to my brother's inappropriate behavior in the public, I finally understood the saying: "Caesar's wife must be above suspicion."