Gustaf is a name of Swedish origin, derived from the Germanic elements "guth" meaning "god" and "frithu" meaning "peace". It was brought to Sweden by the Vikings and has been used in Sweden since the Middle Ages. Gustaf was the name of several Swedish kings, with the most notable being King Gustav Vasa, who reigned from 1523 to 1560 and is credited with leading Sweden's rise as a great power. The name Gustaf is often shortened to Gus orGust for informal use. It has also inspired various place names in Sweden, such as Gusum and Gustavsberg. In English-speaking countries, the name Gustaf is sometimes used as an alternative to its more common equivalent, Gustaf.
"The name Gustaf experienced significant fluctuations in popularity over the years, with a notable surge in the early 20th century, peaking at 24 births in 1915. However, it has generally been quite uncommon, with fewer than 10 births per year for most of its history."