A correction, and a few additions:

ORD stands for Orchard Field, not Orchid. See this link for some interesting history of O'Hare. http://www.airwise.com/airports/us/ORD/ORD_07.html

Contrary to popular belief, SFO originally designated "San Francisco - Oakland" before OAK had its own airport. There are apparently several (gratefully ineffective, so far) folks out there who want to re-designate SFO as SFI (perish the thought!)

Spokane International (GEG) is another airport ID'd by the local military base (Geiger Field).

. . . and JFK was New York International Airport between 1948 and 1963 and before that was Idlewild, hence the designation IDL (and the (in)famous lyrics: "There's a scout troup short a child, Khruschev's due at Idlewild. . . Car 54 Where Are You?)