Louis-Lucien Bonaparte, in 1869, classified it as Northern Upper Navarrese Basque and, within that, in the Guipúzcoa sub-dialect and Irún variety. In a 1778 document, it is stated about Basque in Fuenterrabía:
“Until now it has not been d Romanized, nor is it conceivable that it could be, because the native language, common and current, is Basque, which all or most understand, both inside and outside the walls, and in many farmsteads, and in all of these; and those who only speak Castilian are very few and limited to the king’s dependents, as it is a garrison town, and no doubt for them the religious custom of preaching in Castilian was introduced for their spiritual nourishment, but without omitting Basque…”
Sources: Various, Geografía Histórica de la lengua vasca, Auñamendi, 1960, vol. I, pp. 67-102.
In the first third of the 19th century, Añibarro included it, for preaching purposes, in a list of strictly Basque-speaking towns (op. cit., pp. 44-60). By 1970, the number of Basque speakers had risen to 6,800, representing 65% of the total population (Pedro de Yrizar: “Los dialectos y variedades de la lengua vasca,” sep. Boletín de la Real Sociedad Vascongada de Amigos del País, 1973, p. 42).
Regarding the use of Basque in 1778, see also Satrústegui: “Plática vasca del año 1778 en el proceso de Fuenterrabía,” Fontes Linguae Vasconum no. 32, pp. 287-302.
In May 1979, the new Ondárroa City Council decided, by 13 votes in favor and two abstentions, that the minutes of municipal plenary sessions would be drafted in Euskara without a Castilian translation. This unprecedented decision broke a tradition only surpassed by some letters from the Hendaye City Council on fishing matters preserved in the archives.