I'm pretty sure the name Janet came to the English from the French. The French like to add the "ette" when something is small, cute, or young. So, "Janette" pronounced more like "Jean-ette" in French became the English nickname (or pet name) for a young girl named "Janet." The English just dropped the "te" at the end. It comes from Jane, but no one has ever called me that.
In 2018, 56 is the most common age for an American (U.S.) Janet who is registered female with the Social Security Administration. It is the 100th most common female first name for living U.S. citizens.
― Anonymous User 10/15/2018
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The name Janet was given to 153 girls born in the US in 2015.