Wikipedia
Ushana
Ushna (उशना) or Yat (याट) was, in Hindu tradition, a brave king of Yadava Vansh, born after three generations of Maharaja Shashabindu, who was born after six generations of Yadu. It is said Maharaja Ushana performed one hundred Ashvamedha Yajnas and received the title of yat.
According to the historian Ram Lal Hala, the word Jat is derived from word 'Yat'. The king 'Yat' (Ushana) was in Chandravanshi, an ancestor of Lord Krishna. The Jats are descendants of King Yat.