In Navarre there is a Valley called Guesálaz/Gesalaz, and the pass the Salado River, there is also a salinas, Salinas de Oro. Here, the meaning seems to be the opposite: salt water. The same thing I found in the seaside resort of Zestoa. Apparently, in its origin, medicinal water, salts, was found and was put into operation on a source of the hamlet of Gesalza. I don't know if you have any explanation for these shapes apparently contrary to the expected sense. I write from a tablet that will not let me do so in Basque.