These names are examples of reduplication, a common theme in Australian toponymy, especially in names derived from Indigenous Australian languages such as Wiradjuri. Reduplication is often used as an intensifier such as "Wagga Wagga" many crows and "Tilba Tilba" many waters.
The phenomenon has been the subject of interest in popular culture, including the song by Australian folk singer Greg Champion (written by Jim Haynes and Greg Champion), Don't Call Wagga Wagga Wagga. British comedian Spike Milligan, an erstwhile resident of Woy Woy, once wrote "Woy it is called Woy Woy Oi will never know".