The region of Númenor ruled by Hallatan (UT/197). Its initial element is most likely the prefixal form hyara- of hyarmen “south”. The second element looks like a derivative of the root √STOR “steadfast” (PE17/186). It may also be related to torna “hard”, whose superlative form anastorna indicates that it might be from the same root (PE17/56). If so, the name mean might something like “*South Fastness”.