Other threads have much more information; this is perhaps the poorest. See link to Lyr. Add: Guantanamera (24), at top of thread.

In that thread, post by Dicho, 27 Mar 02, gives the words to the "Versos Sencillos" (Simple verses) by Martí (1891). No mention of Guantanamera in his verses.

Joseito Fernandez (Diaz) made his song in 1930-1932. Julián Orbón adjusted the song and added the verse by Martí. Their final revision is given in the post cited above. The estribillo (chorus) is theirs: Guantanamera, guajira guantanamera, (2x).
The tune is 19th c., slightly varied, from the region of Guantanamo; a guajira- style of the region, rustic, rural- and dedicated to "una guajira," a woman of the region.
Celia Cruz and others replaced the third verse with another Martí verse, not from "Versos sencillos."

Some of the verses have allusions to Castro's campaign to free Cuba from the oligarchs.
Tiene el leopardo ou abrigo
en su monte seco y pardo;
yo tengo más que el leopardo
porque tengo un buen amigo.

Y para el cruel que me arranca
El corazon con el vivo
Y para el cruel que me arranca
El corazon con el vivo
Cardo ni ortiga cultivo
Cultivo la rosa blanca.
(And for the cruel one who would tear out this heart with which I live, I cultivate neither thistles nor nettles; I cultivate a white rose.)

The post points out that Angulo, a student of Orbón, went to New York and showed the song to Seeger and Joan Baez. The song was redone and came out in an album, "Spanish Album, The Sandpipers," authors Martí, Angulo, Seeger; with no mention of either Joseito Fernandez or Orbón- THEFT, pure and simple.

The essentials of the history have been recast from the article by Natalio Galan by Maria Argelia Viscaíno.
http://www.meetinglatino.it/pagine/cuba_musica/s_guantanamera.htm
La Guantanamera
The much longer article by Natalio Galan parts I-IV are found at: http://www.cubanmotives.com/Espanol/Articulos/Maria_Viscaino/La%20guantanamera.htm

The heirs of Joseito Fernandez finally reclaimed title in 1985:
http://www.elviraz.com/articulo506.htm
La Guantanamera
This article also mentions others who contributed verses to variations.

Note- the reference to 'octosyllabic' is confusing since some lines have nine or ten syllables if pronounced correctly.