“Jiggy” is a term meaning to be cool and trendy. It’s often associated with a style of dress, and in the context of this song means dancing effectively and also making a name for yourself. It also became a term for sex.
Although Will Smith wrote the majority of the lyrics the song was produced by the team of Jean-Claude Olivier and Samuel Barnes, who were known as Poke & Tone. Poke came up with the title “Gettin’ Jiggy Wit It’. The title stuck, and when the song became a huge hit, “Jiggy” made the leap from street vernacular to the popular lexicon.