What is "yaudheya"

Yaudheya or Yaudheya Gana was an ancient confederation who lived in the area between the Indus river and the Ganges river. They find mention in Pāṇini's Ashtadhyayi and Ganapatha. There are other references to them namely in Mahabharata, Mahamayuri, Brihatsamhita, Puranas, Chandravyakarana and Kashika. As references are spanned from writings of early period to the medieval period, the chronology of Yaudheyas perhaps spans from as early as 500 BCE till 1200 CE. They were in zenith of their power from about 200 BCE to 400 CE.