A popular Havana radio host in the 1940's, Jose Fernández Diaz known on the radio as Joseito Fernández, created the famous refrain, which he would sing on his daily radio program.
It seems that he had a crush on a girl who worked at the station, who happened to be from Guantánamo. The girls of Guantánamo were known for their beauty. There was a lot of intermarriage between the Spanish settlers and the Scottish and Irish pirates who were based there. Many Guantanameras have beautiful green eyes! Several songs have been written about the Guantanameras and their rare beauty.
A guajiro is a person from the country a farmer, peasant, or rancher. Thus "Guantanamera, guajira" means a girl from Guantánamo, a country girl.
Each day Fernández would sing the song to woo the girl of his dreams. The verses were usually humorous and he made them up as he went along. The only thing that stayed the same was the refrain. Who first added the words of the poetry of José Martí (Yo soy un hombre sincero...) is still a matter of debate.
The American singer, Pete Seeger, may not have been the first to add the lines from Martí, but he was the most successful with his recording of the song. Julian Orbon, Hector Angulo and Pete Seeger are credited with the adaptation of the lyrics on the album.