In Hebraic thought, the thing that is named is subject to the one who named it. The Teacher here reminds the readers that all of creation, including mankind, is subject to God.
Even the word “man” is what was assigned to us when God created our first ancestor, Adam. There are those who believe they are self-made men or women. The truth is none of us are self-made. And neither is anything in all of creation. All of it is subjected to God’s authority whether that is recognized or not.
The Teacher then reminds us that because of that, we cannot argue with One stronger than us – namely God. He reiterates that truth by the expression in verse 11. Using more words against a stronger foe is vanity or useless. We cannot win in our dispute, so more arguments are just wasted words. God will have the final say in all our lives.