What is "jashon"

According to The Book of Mormon, Jashon referred to a land and a city in the land northward near the land of Antum. Jashon is mentioned in only two verses: . The Nephites retreated before the Lamanites until they reached Jashon. From Jashon, their captain, Mormon, went to the land Antum to fulfill the promise made in his youth to Ammaron to record a history of his people.