Take our virtual guided tour of Horcajo de la Sierra and Aoslos
It is believed that the origin of the name "Horcajo" is related to the village's geographical location, since its etymological roots refers to "the confluence of two rivers or streams, or the point of union between two mountains or hills".
Horcajo's origin is unknown, but there is evidence of its existence as early as the XIV century, its name appearing in King Alfonso XI's well-known Montería book ("Libro de Montería").
The original settlement is found in the lower part of the village, where it is still frequent to find the remains of old constructions. According to a study, the origin must have been that of an ancient Torre-Fuerte (tower), surrounding which the old village must have been built. The tower would have been later transformed into a bell tower, and then attached to the church.
Horcajo's history is closely related to that of the Señorío de Buitrago, whose town was for centuries the capital of a community of several villages, sharing a common history, as well as a common economy, tradition, folklore, etc...
The Villa de Buitrago and the 32 villages of its jurisdiction, Horcajo being one of them, made up the Señorío de Buitrago and the Comunidad de Villa y Tierra. All of them looked for the common good, and were governed by common general regulations. They were organized in groups known as Cuartos (quarters), each having one representative. Horcajo was seat of a Jurisdictional Quarter, to which the villages of Piñuecar, La Acebeda, Bellidas and Madarcos belonged.
According to the Moneda Forera census, which dates back to 1554, 85 neighbours lived in Horcajo (a 'neighbour' was considered to be a family unit, so that the real number of inhabitants would be four or five times that number). Later on, in the 1656 and 1670 registers, there were 35 and a half and 27 neighbours respectively.
The population grew again in 1782, reaching 80 neighbours, and 87 in 1850 (equivalent to 342 "souls").

The name "Aoslos" has a harder interpretation, but it could have derived from the Celtic term "coslo", meaning hazel tree, that would have evolved to "caoslo-aoslo", that is, "hazel tree place".
It was funded some time after Horcajo was born, by a few of Horcajo's own inhabitants that established their homes there forming a new settlement. The oldest references of Aoslos date back to the XVIth century, describing it as being located close to a hermitage dedicated to Santiago apostle that no longer exists. The next reference to Aoslos can be found in Ensenada's property register, (XVIII century), where it is already referred to as a district belonging to Horcajo.