According to Nate Silver and Allison McCann, it’s pretty easy to peg someone’s age by their first name -all you need are Social Security name records and actuarial tables. Ha! That’s a lot easier for someone like Silver, who lives and breathes statistics. However, they’ve already done the research on quite a few names for our convenience. You can guess that women named Mildred, Opal, Ethel, Gertrude, or Beulah would be elderly, and that kindergartens are full of girls named Eva, Mia, Sophia, Ella, and Isabella -and you’d be right. See tables with the oldest, youngest, most spread-out in time, and most common names for both men and women, and some outliers like Violet, who might be elderly or might be young, but probably wouldn’t be middle-aged.
Of course, there are some names that are easier to peg than others, but they aren’t all that popular. If you ever run into a woman named Cher, Layla, Shania, or Madonna, pity them, for they will never be able to lie about how old they are. -via the Presurfer
And "Mary"? Did they survey convents?