Twanyirika is a named spirit-being of Arrernte (Arunta) religion first documented by Baldwin Spencer and F. J. Gillen in their classic Central Australian ethnographies. During the lartna circumcision ceremonies, initiated men whirl bullroarers around the darkened ceremonial ground, and women and children are taught that the roaring sound is the voice of Twanyirika, a powerful spirit who takes the newly circumcised boy away into the bush until his wound heals, and who is said in some accounts to kill the boy and bring him to life again as a man. Initiated men learn during the rites that the sound is produced by the bullroarer itself, so that belief in Twanyirika marks the boundary between the initiated and the uninitiated. The figure was widely discussed in early twentieth-century debates on Australian religion, notably by Andrew Lang.