The people who are known today as "Apache" were first encountered by the conquistadors of the Spanish crown, and thus the term "Apache" has its roots in the Spanish language. The Spanish first used the term (Navajo) in the 1620s, referring to people in the Chama region east of the San Juan River. By the 1640s, they applied the term to southern Athabaskan peoples from the Chama on the east to the San Juan on the west. The ultimate origin is uncertain and lost to Spanish history.