The name "Mont Jardín" likely comes from a popular interpretation of “Mons Garzini,” linked to a legendary Charlemagne victory in the History of Turpin.
The term "Garzin" remains unclear but is possibly connected to “Garcianis,” a patronymic of Sancho Garcés I, the Navarrese king who seized Deyo from the Banu Qasi and was buried in San Esteban.
The fortress likely became a "tenencia" or honor under the bishops of Pamplona, including nearby villages like Adarreta, Azqueta, Igúzquiza, Labeaga, Lúquin, Urbiola, and Villamayor.
[3] The noble Medrano family, ancient lords of Igúzquiza, ricohombres of Navarre, became the governors of the famous Monjardín castle, whose prodigious cross is said to have been collected by one of these knights when it appeared to one of his shepherds.
In the early 16th century, Don Juan Vélaz de Medrano y Echauz, sixth of the name, was the alcaide of the castle of Monjardín.
After the conquest of Navarre by Ferdinand the Catholic, the castle fell under the constable count of Lerín, exempting it from demolition orders in 1516 and 1521, and later passing by marriage to the House of Alba.