Flair got it from...
"Nature Boy" Buddy Rogers
[...] He bleached his hair
and was given the moniker "Nature Boy" by promoter Jack Pfeffer after the popular jazz song.
The Song...
"Nature Boy" is a song by Eden Ahbez, published in 1947. The song's melody is based on a Yiddish tune, "Schweig Mein Hertz" ("Be Still My Heart").