Interesting read [full article here] in the New York Times about "gender fluid" names. Do you know that Shirley is a historically male name?
The article talks about the notion of "crowding out" ...
"Not long after a boy’s name catches on with girls, parents shy away from christening sons with it. “We crowd them out,” Nilsen says ... Through 1955, “Leslie” consistently appeared among the 150 most popular boys’ names. About a decade earlier, it began to catch on among girls. And the “crowding out” Nilsen mentioned took place ... Dana, Carol and Shannon met similar ends."
For the record, my son's name is Henry.