This name was taken from map drawn in 1566 by Bolognini Zaltiere (fl 1550-1580)[1]
"The late Sir Conrad von Graz found the word on a reproduction of an old Spanish map of parts of Western North America, and the word was placed (very very approximately) where Alberta is today, and he thought it sounded good as a name for the proposed region." (quote from Thorvald Grimsson, taken from the Avacal Circus. The territory was also shown on other late 16th century maps of North America, such as the 1562 Gutierrez map and the 1570 Ortelius atlas, Theatrum Orbis Terrarum.