Meaning of once brutos by Anónimo

"It is an Oncebrutos" It is an expression that both my mother, my neighbor and her mother-in-law used to qualify someone, even of close kinship, as that he was very donkey, animal, very brute, etc. , even the mother-in-law of my neighbor when sometimes she wanted to reprimand a grandson who made some mess and who did not fall far beyond in addition to this expression used that of "Be still mastiff of ganao" . I get the impression that "oncebrutos is used in the North of Castile but I do not locate where, I say it because recently I was in Oña and in a street I saw the sign of a hostel restaurant called "Once Brutos" so I say that the same is an expression of that area, which I would like to know because it would indicate that some of our ancestors, in distant times, they came from there and to earn a living they came to a village near Madrid where they settled.