A cheechako is a person who is a
tenderfoot, a
newbie -- the term dates from the
Klondike Gold Rush of the
1850s in
Alaska and the
Yukon.
Daniel Pinkwater quotes a friend living in Alaska as saying the word is an
Upik pronunciation of "
Chicago," but I can find no confirmation of this, and in fact a web site I found explains the word as "combining the
Chinook Indian word 'chee,' meaning new, fresh, or just now, with the
Nootka Indian word 'chako,' which means to come, to approach, or to become."
But whatever the source, the new people coming up from points further south, inexperienced in mining or surviving Alaskan winters, were called "cheechakos," and the word found its way into the works of Jack London and Robert Service, and it's still used in the area to describe newcomers. (It also seems to be used as a name for stores and tour companies.) After a certain amount or time or experience, one becomes a "sourdough."
Sources:
http://www.lifeinak.com/glossary.htm
http://www.zianet.com/sunny/html/untitled_2_3.html
Daniel Pinkwater, Hoboken Fish and Chicago Whistle, 1999, page 88.