Youth is wasted on the young.
After the Romans extended their empire throughout the Mediterranean they appropriated the Greek sign Upsilon to be the last letter of their alphabet -- which until then had been the X. Due to its recent arrival in the alphabet, the Y has had little time to develop its personality and has had virtually no impact on the historical record. With the unique distinction of not initializing any Greek or Roman deity, it is neither the initial letter of any first, middle, or last name of any American President or Vice President in history, nor is it the initial letter of any current member of the House of Representatives or Senate.
Given the lack of male role models it's not surprising that girls are thirty times more likely to have a Y name than boys are. As the initial letter of the word yes, yep, yippee, yee-hah, yippee, and yeah, Y names seem infused with a air of enthusiasm and zeal. Additionally, because of the human tendency to associate high-frequency sounds with friendly and reassuring situations, words that end with the high-pitched tones of the Y typically convey a feminizing or intfantilizing tone: coy, play, baby, happy, downy, rosy, sunny, cozy, sassy, gay, and shy.
The Y is used in algebra to denote an unknown quantity (along with letters X, and Z), and also initializes an unusually high number of words that pertain to the passing of time and measurement in general -- yesterday, young, year, yardstick, yet, yonder, and youthful.