I have just recalled that it was called Borough English, about which Encyclopedia Britannica has this to say:
"Borough-English, the English form of ultimogeniture, the system of undivided inheritance by which real property passed intact to the youngest son or, failing sons, to the youngest daughter. Ultimogeniture was the customary rule of inheritance among unfree peasants, especially in southeast England. Its antiquity is uncertain, but it is first mentioned in the 12th century. “Borough-English” became the accepted legal term for the custom after a famous case in 1327 drew attention to the fact that in the French borough of Nottingham, which had grown up beside the English borough, land passed to the eldest son, whereas in the English borough it passed to the youngest son. As a system of undivided inheritance, borough-English applied mostly to unfree peasants and, like primogeniture, acted to preserve the manorial unit; among free peasants, land tended to pass by equal division among sons and daughters. The custom continued in many rural manors until abolished by the Administration of Estates Act of 1925."
