The word ekklesia was a word that had been ingrained in the Greek culture for at least 400 years before Jesus used it. To the Greels the ekklesia was not some loose grouping, but rather a formal assembly whose purpose it was to make the most significant decisions for a city-state. The ekklesia was formed only of makes over the age of 20 who had actually fought in defense of the city-state. It was structured, hierarchical and obligatory. Those failing to assemble when called (the root of the word) were subject to receiving public beatings. Those arriving late would be struck with whips dipped in paint so that they would wear their shame (stripes). The ekklesia were the only ones who could impose the death penalty, declare war or remove and try high civil officials.
It is hard to believe that the Word of God would not know the meaning of this word.
Peace be with you
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