What is the meaning of "egg" in the idiom "throwing eggs at stones"?

"Egg" in the idiom "Throw an egg at a stone" means (egg).

Throw eggs at stones.

Yang lvren

Explain that touching eggs with stones. Metaphor does not estimate their own strength, bring about my own destruction.

The source "Xun Zi Yi Bing": "If you are a demon, if you throw stones with eggs, it is called boiling around."

Formal idioms

This usage is formal; As predicate, attribute and object; derogatory sense

Synonym throwing stones at eggs is more than one can chew.

Ex.: Liu Yuzhou doesn't know much, but he is eager to try, just like ~, is he invincible? (Ming Luo Guanzhong's Romance of the Three Kingdoms, the 43rd time)

let blood with a single prick (of the needle)—pierce to the truth with a single pertinent remark