What is "njars"

Njarar or Njars were an ancient Germanic people of Närke, Sweden, that appears in the Scandinavian version of the Lay of Weyland the smith. In the early part of the lay, King Níðuðr is introduced as a king in Sweden:

Níðuðr hét konungr í Svíþjóð. Nidud was the name of a king in Sweden.

Later he is specified as the lord of the Njars:

Þat spyrr Níðuðr, Níára dróttinn, at einn Völundr sat í Ulfdölum; nóttum fóru seggir, neklðar váru brynjur, skildir bliku þeira við inn skarða mána. (Source) When the Lord of the Njars, Nidud, heard That Völund sat in Wolfdale alone, He sent warriors forth: white their shield-bosses In the waning moon, and their mail glittered. (Translated by W. H. Auden and P. B. Taylor)

The Njars probably lost their independence early to the Swedish king at Uppsala, and they are not mentioned by Jordanes in his thorough listing of tribes in Scandza, in the 6th century. There are few mentions of the Njarar/Nerikjar in Old Norse sources, but for exceptions see King of Nerike.