Why do many US Army helicopters (and aircraft) have Native American Tribal names?

Why Army Helicopters Have Native American Names
Note: that title is a bit misleading, as this applied to any US Army aircraft, whether fixed-wing or rotary-wing. Of course, this meant an aircraft that was procured by the US Army. If an aircraft was used by multiple branches of the US armed forces, then sometimes the US Army variant would have its own name, but sometimes be named the same as the other variants. For example, the Sikorsky S-58 helicopter was designated H-34 Choctaw by the US Army, HUS Seahorse by the USMC, and HSS Seabat by the USN (H-34 after 1962). Another example would be the Cessna Model 310, which was used by both the USAF and the US Army, but was designated L-27 / U-3 Administrator for both variants.

Here is a list of most US Army aircraft with a name after 1947:

Native American Tribal names:

• Bell R-13 / H-13 Sioux
• Sikorsky H-19 Chickasaw
• Piaseck H-21 Shawnee
• Sikorsky H-34 Choctaw
• Sikorsky H-37 Mojave
• Cessna H-41 Seneca
• Piper L-21 / U-7 Seneca
• Beech L-23 / U-8 Seminole
• Grumman AO-1 / OV-1 Mohawk
• Hiller VZ-1 Pawnee
• Beech C-12 Huron
• Cessna T-41 Mescalero
• Beech T-42 Cochise
• Beech U-21 Ute
• Bell HU-1 / UH-1 Iroquois
• Hughes HO-6 / OH-6 Cayuse
• Boeing Vertol HC-1 / H-47 Chinook
• Sikorsky CH-54 Tarhe
• Lockheed AH-56 Cheyenne
• Bell OH-58 Kiowa
• Sikorsky UH-60 Black Hawk
• Hughes AH-64 Apache
• Boeing-Sikorsky RAH-66 Comanche
• Bell TH-67 Creek
• EADS North America UH-72 Lakota
• Pilatus V-20 Chiricahua

Other names:

• Hiller H-23 Raven
• Piasecki H-25 Army Mule
• de Havilland Canada AC-1 / CV-2 / C-7 Caribou
• de Havilland Canada AC-2 / CV-7 / C-8 Buffalo
• de Havilland Canada AU-1 / C-137 / U-1 Otter
• Ryan VZ-3 Vertiplane
• Piasecki VZ-8 Airgeep
• Avro Canada VZ-9 Avrocar
• Lockheed VZ-10 / XV-4 Hummingbird
• Ryan VZ-10 / XV-5 Vertifan
• MSU XV-11 Marvel
• Cessna L-19 / O-1 Bird Dog
• Cessna O-2 Skymaster
• de Havilland Canada L-20 / U-6 Beaver
• Stinson L-5 / U-19 Sentinel
• Bell AH-1 Cobra
• Kaman AH-2 Tomahawk

List of federally recognized tribes in the United States - lots to choose from!