Guillermo, of Spanish origin, means "will helmet" or "protected by God". It's a strong and elegant name that has been popular throughout history, often associated with notable figures such as Guillermo II, King of Saxony, and Guillermo Tell, the hero of a Swiss legend who inspired Schiller's play.
"Guillermo had a surge in popularity between 1980 and 1982, with five births each year. It also saw a spike in the early 1990s, with eight births in 1991 and seven births in both 1992 and 1993. The name's usage has been quite consistent over the decades, with an overall total of seventy-four births."