This is only a teaser, you need to read the rest!
Here’s how it works. As women age, their estrogen levels decrease and the ratio of testosterone to estrogen increases. The way I see it, women become more “testy.” For men, the reverse is true. As our testosterone levels drop, the ratio of estrogen to testosterone increases. The effect is that men become for “esty.”
From Laura Wattenberg at the BabyNameWizard Blog
In the early years of the graphs, pet forms like Joe, Sam and Gus show up strongly as given names. That's a window on an age when--despite our impression of stiff, buttoned-down ancestors--fun and informal names like Buster and Birdie were at their peaks. In the middle of the century you see parents withdrawing from both ends of the spectrum and sticking safely to the center. And the past generation shows a dramatic rise in long, multi-syllabic names...turf traditionally ceded to girls. (The girls' counterparts to Joseph, Henry and Edward, for instance, are Elizabeth, Catherine and Margaret.)