The term "Lolita" is a slang term for a sexually attractive or precocious young girl. It originated from the novel Lolita, whose protagonist and unreliable narrator, becomes obsessed and sexually involved with a 12-year-old girl named Dolores Haze for whom his private nickname is Lolita.
Despite similar names, the Lolita fashion and Lolitas/Lolis have no relation to each other whatsoever. Lolita is a style of dressing in a Victorian or Rococo-style era, for adults and teenagers who want to look like children. It originated in Japan, inspired by Lolicon(Pedosexual) art.