The Bunny Girl is a fetish outfit made popular by the Playboy company though the meaning is different in Japan. A popular outfit in cosplay.
The concept of the Bunny Girl was originally made popular in the Playboy Clubs that opened in the early 1960s. The concept was originally called the "Playboy Bunny", the title given to all the models who appear in the nude magazines the company publishes.
The outfit was worn by all the waitresses in the clubs. The outfit is even trademarked in the United States. Though the clubs were originally all closed in the 1980s. The club was revived in the year 2006 in Las Vegas Palms Hotel.
The concept in Japanese culture has lost much of the connection to the Playboy origins. It is more connected with sex appeal in general. In Japan they are just called a "Bunny Girl (banii gaaru)".
The Bunny Girl appearance is quite popular among fetish cosplay. The rabbit is seen as an animal that is timid and requires companionship to live and survive. This most likely explains why the costume is often seen as being worn by a subservient person. Intended to associate the woman wearing it as being submissive and in need of care.
The outfit worn by the Bunny Girl is called the Bunny Suit. The costume consists of a cleavage exposing, skintight leotard; pantyhose, neck-collar with bow tie, wrist cuffs, high heels, and decorative bunny ears and a optional tail. Occasionally, there is a shaped name tag pinned to the waist, and the tail isn't always present in the Japanese version of the Bunny Girl costume.