More info about the name "Jillian"
Jillian is a variant of Gillian. Gillian originates in Latin language and means "daughter of Jupiter". It is ultimately derived from Julius and thus is related to the feminine given name Julia and its variants. In this spelling, Gillian became popular sometime in the 17th century. The famous bearer is Gillian Anderson, an American actress known for her character of Special Agent Dana Scully in the TV series The X-Files.