Billabong comes from Wiradjuri (an Australian Aboriginal language) bilabaŋ, perhaps from bila ('river') + a suffix; borrowed into Australian English in the 19th century. The historical trail runs through bilabaŋ in Wiradjuri. Morphologically, billabong is transparent: it draws on Wiradjuri (an Australian Aboriginal language) bilabaŋ, perhaps from bila ('river') + a suffix. Used as a noun, billabong now means "an Australian backwater or stagnant pool left by a river", so the present definition can be read against the older forms and meanings. The result is a borrowed or transmitted form whose modern spelling carries a compact record of its route into English.