From Russian Аля́ска (Aljáska, “Alaska”), in turn from Aleut alaxsxaq (“mainland”, literally “that toward which the action of the sea is directed”), composed of alag (“pertaining to the sea”) + -sxa (nominalizing suffix, yields 'the objective of action expressed by the root') + -q (nominalizing suffix).
Commonly misattributed to Russian ала (ala) + -ский (-skij, adjectival suffix).