A lost toponym is a name given to a place, which is no longer known or identifiable. For example, in 1618 the crew of the Mauritius explored a river in north-western Australia, which they named Willems Revier ("Willem's River"). However it is not now known which river they explored, so Willems River cannot be placed on a present-day map. Willems River is therefore a lost toponym.
Many Biblical terms for peoples and areas are today controversial or debatable, such as the land of Magog

Magog

Magog may refer to:* Magog , a grandson of Noah in the Old Testament* Gog and Magog, a Biblical pair * Magog, Quebec, a town in southern Quebec, Canada...

, the identity of which is not known today.