In the John Lee Hooker "Bluebird" I believe that he may be calling a USPS truck a bluebird, because he tells the bluebird to "Bluebird, please take this letter down south for me", I have never heard Postal trucks called bluebirds elsewhere, but in the context of the song it makes sense, but also, I'm from Seattle, John Lee Hooker is definitely from the South and our dialects are very different.
Bluebird, please take this letter down south for me.
code word for Cocaine. Etomology: On the Navajo Nation, the Navajo people use Bluebird Flour to make Navajo frybread. Young Navajo cokeheads starting use Bluebrid as a way to refer to cocaine. See related Frybread (reference to crack cocaine)