Over the past 110 years, 593 boys and 705 441 girls have been named Cynthia. The name Cynthia ranks 3171th in the United States among the most common names for boys. For the first time more than ten times newborns were named Cynthia in 1947. The peak of popularity of the name Cynthia came in the 1940s and 1970s. You can see absolute numbers and relative numbers on the chart. Indicators per 100K more accurately assess the popularity of the name.