Here is the answer to your question, as explained by Cecil Adams, World's Smartest Human....
Do women have an extra rib cuz Eve got one of Adam's?
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Dear Cecil:
Is it true that women have two more ribs than men do? If so, could this be the origin of the biblical story about how Eve was made from Adam's rib? And while we're on the subject, what does the word "spare" refer to in "spare ribs"? --Bobby V., Chicago
Cecil replies:
All God's chillun got twelve ribs, Bob. The origin of the Adam's rib story isn't known for sure, but some think it may stem from a Sumerian joke.
Here's the dope: the Sumerians had a myth about a consortium of gods who were busily turning the land of Dilmun into a paradise when one of their number, Enki the water-god, committed a breach of etiquette by nibbling on a newly-created plant. Ninhursag, the earth-goddess, put a curse on Enki, and he fell ill as eight of his vital organs failed. Ninhursag was eventually persuaded to relent, but to cure Enki she had to create eight different new deities to cure each of Enki's ailing organs.
The story bears some resemblance to, and in fact may have been the inspiration for, the Hebrew story of Genesis: the creation, the eating of the forbidden fruit, etc. But here's where it gets really interesting: the Hebrew name "Eve" means, approximately, "she who makes live." In Sumerian, the word for "make live" is ti, which is also the Sumerian word for "rib."
Thus, the name of the goddess created to cure Enki's aching rib, "Nin-Ti," may have been a Sumerian pun, meaning both "The Lady of the Rib" and "The Lady Who Makes Live." The joke was lost when the story--itself much altered--entered the Hebrew tradition, leaving only the enigmatic association of Eve and Adam's rib.
As for spare ribs--known as "sparribs" in the relatively terse seventeenth and eighteenth centuries--they take their name from the Middle Low German word "rippspeer," which eventually became "ribbesper." It was the custom of the Middle Low Germans to sit around their fires roasting pig ribs on a spit or, as they preferred to call it, a "sper" (a word that survives in English as "spar," as in the rib supports of a ship).
Somewhere in the sixteenth century, the two elements of the German word became transposed as it entered English--"ribbesper" became "sparrib." As time marched on, the excessively literal English insisted on disconnecting the "spar," thinking it came from the adjective "spare." Thus another boneheaded blunder became part of the English language, confusing you and keeping guys like me in business.
--CECIL ADAMS