The name Sebastian is of Greek origin and means "Venerable." The origin is the culture in which the name originated, or in the case of a word--the language in which it most appears.
Common nicknames include Seb, Bas, Bash, and Sebby/Sebbie. The popularity of the name increased with the telling of the Biblical story of Saint Sebastian.
Famous Sebastians include actor Sebastian Cabot, Johann Sebastian Bach, composer, and Sebastian Coe an athlete who became a member of the British Parliament. Sebastian Faulks is a British author.
One of the most famous fictional Sebastians is the crab from Disney's The Little Mermaid, whose full name is Horatio Thelonious Ignacious Crutaceous Sebastian. Lord Sebastian is from the television show, Brideshead Revisited and Colonel Sebastian Moran is a character in the Sherlock Holmes series of stories by Sir Arthur Conan Doyle. Sebastian Monroe is a fictional president in the TV show Revolution.