Obviously this has nothing to do with the origin of the word "Mom", but in the American south where I was raised (white), we used the term "Mommy", until we felt we were older, and as the result of our "newfound maturity" had a "Mom" instead of a "Mommy". The choice was conscious, and took a little effort after years of using the first term, but we were far too mature to be heard saying "Mommy" in public!

Thank you.