Here in Delaware it would seem that a "boytoy" is a prostitute. This isn't the case with me!
My username isn't nearly as sexual as it would seem either! The story goes like this:
When i was 17, and a Junior in high school I was dating a wonderful man. As it happened, he was 10 years my senior. OOOooops! (I never got quite around to correcting him when he assumed i was 20). One of my good friends from school, Krystal, found it quite intriguing, and started referring to me as his "boytoy." Well, "BoyToy" stuck, and my immediate circle of friends started to call me BoyToy with regularity (in fact, i'm listed in some of my HS yearbook pictures as "BoyToy").
Some years later i was in college and ran into one of my highschool friends. He couldn't quite remember my old nickname and called me "JoyBoy" by mistake. I thought it was hillarious, and the next time i saw Krystal i told her about it. She too was smitten with giggles, and smooshed JoyBoy together with BoyToy and thus was birthed "JoyBoyToy."