Quote Originally Posted by bad manners
You're wrong here. The stem "яро" means "spring" in Old Slavic. In Russian it is still used in agriculture: "яровые культуры" (the crops that are planted in spring).
Ярослав, Ярослава came from Ярило and слава, Yarilo is an old Slavic god of sun and spring. here is more about Yarilo