Los supuestos precedentes de los vocablos "Euzkadi" y "Euskaria"

Observations on the article by Gárate on Basque toponimy. For Echegaray the word "Euskari" can not have been the origin of "Euskaria". On the other hand, the appearance of the word "Euzkadia" in a poem dated 1862 makes one suspect that the word "Euzkadi" given by Sabino Arana is not a neologism. However, Echegaray says that "Euzkadia" is "Euskaria", a very common word in Basque language, with the substitution of the "s" and of the "r"