The anthem lyrics were written by Sabino de Arana y Goiri while he was in prison (May-November 1902). The text was created to be sung with the music of the old dance ezpata-dantza (dance of spades). A few years later, the Basque musician Cleto Zabala arranged the music. In 1905 the Basque National Party declared the anthem as the Basque National Anthem. The first Basque Government created during the Spanish war (1936-1939) approved it officialy as Anthem (music and lyrics).
After 1939 with the fascist dictatorship in Spain the anthem was forbidden. In 1983, several years after the end of dictatorship and when the Basque Autonomy was re-established, the Basque Parliament approved the anthem, but only the music without the lyrics so the anthem would not be seen as tied to one particular political party or overly religious in nature.
Special thanks to: Xabier Ormaetxea (member of Basque parliament) for some of this information.