Taking in consideration the presence of a great number of water sources in the valley of Rio Pardu, the traces of a human being dating to the prehistoric times can be found there. According to the tradition, Fuliau Serra, a shepherd from Osini, settled down together with his livestock in the locality of Funtana de Lorista. As far as he liked his new home, he made his family, serves and some friends join him. In the course of time, the number of inhabitants increased so much, that Osini community assigned them a vast territory.
According to the writer Giovanni Lilliu, Gairo may have already existed in the times of San Giorgio Vescovo, but nothing stops us from supposing, that it had already existed before, even though there is no documentary confirmation for it, like for the whole Sardinian history of the early Middle Ages. Actually, Gairo was first mentioned in an official document on March 8, 1217.
But it is not its date of birth, because in the document Gairo was mentioned occasionally, so this may show, that Gairo had existed already, and as many people believe, it was situated near the coast. It is supposed, that in the past the populations, which lived on the coast, were constrained to move in the inlands after some Arab invasions, in particular those of caliph Abd al Malik, who after having conquered the North Africa, built a ship fleet in order to point towards the Western Europe.
The Arabic geographer Edrisi, writing to the Norman court in Palermo about the attitude of the Sards during the four centuries of hard struggles, described them as “brave people who never leave the weapons”. In spite of this undoubted bravery, the inhabitants of the valley of Buon Cammino had to move themselves from the coastal zone to more hidden places, in order to face the enemy, that was more numerous and that was used to wars, more united and protected, reducing in this way the possible surprises. The ideal place for it, that permitted them also to remain on the plain, was the valley of Is Meanas, hidden from the sea behind the hill, and, moreover, surrounded by the nuraghes Trunconi and Musciu, and by the plenty of protruding rocks and rocky precipices difficult to traverse, that were excellent observation points and that served as a shelter, where to easily defend.
Downstairs, where the watershed comes close to Rio Pelau, the Gairese built Domusnoas, new homes. They demolished N. S. di Buon Cammino Church, that had been previously situated on the plain of Foddini, and rebuilt it in its present site, completely hidden from the sea. While they cultivated the flat fertile soils of the surrounding zone, their weapons were always hanging on their waist, ready to face the hostile surprises that at anytime could arrive from the sea.
It's believed that the affinities of character, clothes and dialects between Gairo and Tertenia, which are more marked than those between Gairo and Osini, Ulassai and Jerzu (in spite of their closer location), are determined by the neighbourhood of the first two villages during the period prior to the invasions. Actually, there was an ancient rite, that reminded of those ancient relations of neighbourhood between the two villages: when for the feast a statue of Our lady of Good Way had to be transported from Gairo to its church in the countryside, the Terteniese were preferred to carry out that honourable tradition, if they were present.
In the same way the Gairese were favoured to transport the statue of Saint Sofia from Tertenia to its church. Only a long and integrated neighbourhood could have generated such united relations between the two populations, which was possible only near the coast, where the two territories are still bordering. On the contrary, the coastal territories were and are separated from the mountainous territories of Osini, Ulassai and Jerzu.
According to the tradition, the inhabitants of the both villages left the coast in two different periods, but, by sheer coincidence, they all found a place to settle down near the fold of an Osinese, who, according to the Gairese, was the above-mentioned Fuliau Serra. That suggestive rite, that united the two populations in friendship, was, probably, born exactly when the bitter destiny constrained them to separate and to move away from the sea, intending to hold that ancient and friendly neighbourhood in remembrance.
The fight to the death between the Pisans and the Visconti for possession of the Eastern Sardinia, from Gallura to Cape Carbonara, which started in 1258, constrained the Gairese and other populations, settled down in the plain of Sessei, to escape toward the inlands and to wander for some time in search of a place for a new settlement. However, the Gairese, unlike Loceri and San Pietro, managed to settle down in few years: in fact, the town of Gairo was officially registered by Pisa for fiscal aims as far back as 1316. The new town of the time (which is today abandoned and called Gairo Vecchio) was founded, as mentioned above, close to the fold of an Osinese in the mountainous zone of Funtana ‘e Lorista.
At that time, it was, probably, a small village, but having a church dedicated to Sant'Elena Imperatrice. Anyway, considering the fertility of the plain's soils the Gairese, even with many difficulties (which will be described below) managed to keep them up to the present days.
The strangers were fraternally welcomed and invited to settle beyond the stream, which was later called Arega Piras. According to the tradition, later the women of Ulassai built the church consecrated to the Holy Spirit.
The only condition made to the newly arrived was to recognize as the principal one Sant'Elena's church with all the consequences, even those religious: the processions that started from the Holy Spirit church couldn't cross the intermediate stream, while those of Sant'Elena's church, as a sign of its superiority, could do it.
The period following the removal from the plain of Sessei to the mountains was the time of poverty, not only due to the loss of the personal goods and houses, left by people in a hurry under the pressure of the Pisan troops, but also due to the confiscation of the territory of Sessei, which Pisa had expropriated in its state property. In 1324, Sessei passed from Pisa to the Crown of Aragon, that conquered the island that year, and then to Berengario Carroz, together with the whole Ogliastra, including Gairo.
According to the tradition, a countess of Quirra donated that territory to a woman from Tortolì, Polea Carta. She may have given it again to the Gairese. In acknowledgement of it she was given a pension and honorable regards, like a chair in the church while the others were sitting on the floor or remained on their feet. One of her successors tried to recover the territory through a lawsuit, that finished on October 11, 1580 in brothers Andrea and Francesco Ghigino's favour, who were legitimate heirs to Polea Carta, and thus, they kept the propriety of it.
But the same sentence seems to deny the fact of donation of the land in favour of the Gairese by Polea Carta. They appeared to be simple tenants of the land, as it was also stipulated in the sale agreement, concluded on October 31, 1608, between their mayor Giovanni Piras and the cousins from Tortolì Sebastiano Ghigino and Giorgia Carta. Probably, it wasn't a real transfer of ownership, but an usufruct, with which Polea Carta left the land in the property of their inheritors, reducing the donation to a continuous usufruct by the Gairese', making them pay her an annual pension of 40 liras, while she was alive, and then to her inheritors. In any case, after having received those annual pension for many years, Carta's inheritors decided to sell Sassei.
The Gairese, in their turn, seized the opportunity to buy it. On September 20, 1608, a meeting between the village's heads of the families was held, in order to elect mayors invested with the power to make a deal on behalf of the town. The elected to make the purchase were Giovanni Piras and Giovanni Mulas, who had the possibility to act separately.
In fact, it was mayor Piras who went to Tortolì on October 31, 1608, to discuss the sale agreement. It was agreed that within three months the two parties had to go to Cagliari, the capital of the territory at the time, to stipulate a real bill of sale. But this happened only on March 14, 1616, because after the death of Giorgia Carta long procedures had been necessary before Ghigino finally managed to obtain the necessary authorizations to act on behalf of the younger children, the inheritors of the wife, and also maybe because Gairo could not afford to pay the annual rates of 500 liras.
In the bill of sale it was clearly stipulated that THE WHOLE LAND OF SESSEI was sold by Ghigino and bought by the Gairese, specifying below its borders. The towns of Gairo and Cardedu, which became autonomous in 1984, are still its proprietors, even though after numerous legal peripeties.