Meaning
The idiom "out of the mouths of babes" means that young or inexperienced people may surprisingly say something clever or wise. It highlights the unexpected wisdom or cleverness that can sometimes come from young, innocent voices. It's often used humorously when a child makes an insightful observation.
Origin
The idiom has biblical roots, and is derived from Psalm 8:2, where "God" establishes strength "out of the mouth of babies and sucklings". Jesus also referenced this in Matthew 21:16 when children praised him.
- Source: dear Google with editing
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We are all parents with smart and funny children, I think 
.
I saw one good story by 笑壇壇友小二哥李白 and would like to share it here (with his permission of course 
):
Some years ago, he had an interesting conversation with his young son who was 6 or 7 at the time.
He asked the famous question: "So, which one comes first, Chicken or Egg?"
His son answered quickly without hesitation: "Easy, Chicken comes first."
He was surprised and asked: "Why"
His son: "Because C comes before E."
- https://blog.wenxuecity.com/myblog/57813/201112/15209.html
Ahh, what a clever young man, and a perfect example of "out of the mouths of babes"!!!
Wish you all a happy Easter Sunday 
