Trillian is a
fictional character in
The Hitchhikers Guide to the Galaxy series by
Douglas Adams. Trillian is an
Earth woman who is picked up by
Zaphod Beeblebrox. The character's Earth-name was Tricia McMillan. The nickname "Trillian" was given to her by Zaphod.
The Trillian instant messaging software was named after this character.