A dim-witted person who does not know what they are doing, and if they manage to do anything right, it is only because they were helped by an espejeño (castreño and espejeño refer to residents of the neighboring towns Castro del Rio and Espejo in Cordoba, who share a local rivalry).
That is where the phrase "you are dumber than a castreño" comes from.
Also known as a casqueta, this refers to a resident of the town Castro del Rio. People from this town have a reputation for being clumsy or dim-witted, which led to the common insult 'you are dumber than a Castreño'. (Castro del Rio is a municipality in the province of Cordoba, Spain).
A stereotypical character from the countryside of Cordoba, known for being rude and never greeting people they know. They have a characteristic walk as if they are stepping on their own balls. Physically, they are said to have their necks twisted backward from constantly looking toward the neighboring town of Espejo to see if they can learn anything useful. They also go by the nickname Caquetas. (Castro del Rio and Espejo are rival towns in the province of Cordoba, Spain).
They have been the best since way back: even the Marquise of Espejo used to blow the Marquis of Castro. They are the ones who rule in Espejo and Nueva Carteya, and Espejo stinks (refers to the residents of Castro del Rio and their historical rivalry with neighboring towns in the province of Cordoba).
A guy from Espejo is a blockhead, but a Castreño has a big head on his dick.
A person born in or living in the town of Castro del Rio, Spain.
A Castreño doesn't call your cell: he gives you missed calls so you call him back. A Castreño doesn't fall: he takes a nasty hit. A Castreño doesn't fall in love: he gets totally hooked. A Castreño doesn't try to convince you: he nags you. A Castreño doesn't make plans with friends: he meets up with his buddies. A Castreño isn't brave: he's got balls or ovaries. A Castreño doesn't just go for it: he gets carried away. A Castreño doesn't get drunk: he gets fucking trashed. A Castreño doesn't fail to understand: he just doesn't get it. A Castreño doesn't go to Carrefour: he goes to Eroski (a supermarket chain). A Castreño doesn't turn his back on you: he tells you to fuck off. A Castreño doesn't caress: he gets handsy. A Castreño doesn't bother you: he talks your ear off. A Castreño doesn't stay awake all night: he goes on a gaupasa (an all-night party). A Castreño doesn't drink beer: he drinks Kalimotxo (red wine and cola). A Castreño doesn't work: he grinds.