Alert: Ribald Content
Although there doesn’t seem to be anything definitive in mainstream academia, I recently heard on YouTube that the honorific "Sir" in ancient Sumerian* meant "Big Snake"; conjuring up images of men in antiquities greeting each other with a hearty, reassuring, or perchance an ironic "Good day to you, Big Snake"; perhaps grasping each other's members as aboriginals were wont to do before the humanity was purged of that primal behavior. If true, this would have been an endless source of amusement and stife as men jockeyed for position.
There is simply no equivalent for women, unless it would be, "Ma'am, I greet your mammaries."
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* "The Sumerians lived in Mesopotamia around 4000 BC. Mesopotamia – or the Fertile Crescent – was a region in the Middle East between the Tigris and Euphrates rivers, in the territory of modern Iraq, Iran, and Syria." Source: https://en.wikibooks.org/wiki/Wikijunior:Ancient_Civilizations/Sumerians
It has been known as the cradle of civilization.
Caption: Did Sir Used To Mean Big Snake In Sumerian?
by Annmarie Throckmorton 2019