Sometimes you don’t have to roar to get attention; you need just three letters to land on something great. Leo dates to Roman times and was the name of popes, saints, emperors, and kings. For stargazers, Leo is the fifth Zodiac sign and a constellation shaped like a lion. Like Milo and Theo, Leo ends with an appealing O sound. One of many nicknames elevated to first-name status, it can serve as a nickname for Leonardo, Leonard, Leopold, and Leon, or it can stand on its own. Javier Bardem and Penelope Cruz named their son Leo Encinas Cruz in 2011.