According to the Helicopter History site, traditionally, Armed Forces choose a subject to give name to its ships, airplanes or vehicles.

Here is some information by the site:

"The U.S. Army aviation began in Ft. Sill, Oklahoma prior to moving to FT. Rucker, Alabama. Ft. Sill is located in the heart of many native American reservations and in honor of the location they decided to name helicopters after the various Indian tribes. The one exception is the Bell AH-1 Cobra which was named such because the army did not want to offend the native Americans by naming a gunship after an Indian tribe and have the be percieved as an insult. Shortly thereafter many tribal leaders inquired as to why the Army stopped naming helicopters after Indians. When the reason was explained the leaders stated that there are many aggressive Indian tribes that are fit to name a gunship after which was where the Apache, Kiowa warrior, and formerly the Commanche all got their names from."

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