The Wayilwan ethnonym is derived from their word for "no" in the Ngiyambaa language, (wayil/weil/wail).
[1] Like other Ngiyampaa people such as the Wangaaypuwan, they also referred to themselves according to their home country.
Wayilwan country covered 5,000 square miles (13,000 km2), running along the southern bank of the Barwon River from Brewarrina to Walgett, and along Marra Creek and the Castlereagh, Marthaguy, and Macquarie rivers.
Their southern frontier was at Quambone and in the vicinity of Coonamble.
[1] The Wayilwan were divided into kin groups, one of which is known: the Waiabara.