Wordorigins.org

The name of the 49th US state comes to us, via Russian, from the Aleut alakshak or alaeksu or any one of a number of spelling variants. The Aleut word is reported as meaning either mainland or peninsula.

The form Alaska was in common use by the time of the US purchase of the territory from Russia in 1867. The official name was suggested by Senator Charles Sumner under the misapprehension that the word meant great land.

(Sources: Illustrated Dictionary of Place Names; Webster’s Third New International Dictionary)