Lit. 'co-ploughing'. Modern term for the practice of AS settlers of working together in groups larger than the family. A plough-team of eight oxen was too costly for one family to own and maintain; the heavy plough itself, the caruca, was also expensive. Thus, although large fields were divided up, they were worked co-operatively. [< Lat. aro = to plough]
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.