Interesting, check out Madonna. The name got a second peak thanks to MTV videos ;<)

http://rhiever.github.io/name-age-calculator/index.html?Gend...

Or Elvis whose popularity as a first name looks like a roller coaster.

http://rhiever.github.io/name-age-calculator/index.html?Gend...

Kathy is almost as tight of a peak:

http://rhiever.github.io/name-age-calculator/index.html?Gend...

My point is, the tightness of the peak might have nothing to do with Ms Spears.