Its source is a Latin expression meaning "Sixth."
This boy's name was used in Latin.
In ancient Rome the praenomen, or first name, was often ordinal. Other similar names that are still in use include Quintus (fifth), Septimus (seventh), Octavius and Octavia (eighth), and Nona (ninth). These names either signified the birth order of the bearer or his or her birth month.
Sixtus I - V
Five Roman Catholic popes served under this name, from Sixtus I (115-125) to Sixtus V (1585-1590).
Sixtus V (1585-1590) reorganized the papacy, limited the number of cardinals whom he grouped into congregations (see list of Religious Leaders)