Findmypast.com said its study of U.S. Census data said social changes during the past 72 years may have led to more frequent changes in the popularity of girls' names than boys' names.
"Women's role in society has seen a revolution since 1940", spokesman Brian Speckart said. "Men's role has changed too, though far less."
The Web site said the top 10 girls' names from 1940 have fallen an average 707 places in the rankings, while the top boys' names from the year have dropped an average of 104 places.
Notable deaths of 2014 [PHOTOS]
iPhone 6 smugglers abandon 130 in Hong Kong