Meaning and Name Origin
Gustus \g(u)-stus, gus-tus\ as a name for boys is of Scandinavian origin, and the meaning of the name Gustus is "royal staff; staff of the gods". Gustus is a variation of Gustave (Scandinavian): a royal name in Sweden. A name for kids that is only scarcely used.
Gustus is an uncommonly occurring first name for males but a somewhat prominent last name for both adults and children (#47176 out of 88799, Top 53%). (2000 U.S. Census)
Below is a graphed comparison of the popularity of the boy name Gustus and related names. Popular variation forms of Gustus (#unlisted) listed in the Top 1000 are Gus, Guss, Gustaf, Gustav, Gustave and Gustavo (#482 in 2014). Usage of these boy names was at its peak during 1880-1889 and has become much less since, with the versions Gus, Guss, Gustaf, Gustav and Gustave becoming somewhat dated. Gustavo (#482) is the most chic boy name here. (2014 Birth Statistics)
A recommended similar baby name is Justus. Like Gustus, this name is not frequently used.