The same as “borough English,” under which lands descend to the youngest son. By Gavelkind, land passes to all sons in equal proportions.
If the father has no son, then (in cradle-land tenures) the youngest daughter is sole heiress. If neither wife, son, nor daughter, the youngest brother inherits; if no brother, the youngest sister is heir; if neither brother nor yet sister, then the youngest next of kin.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894