heptarchy (n.)

1570s, from Modern Latin heptarchia; see hepta- "seven" + -archy "rule." A group of seven kingdoms; especially in English history in reference to Anglo-Saxon times (Kent, Sussex, Wessex, Essex, Northumberland, East Anglia, Mercia). "The correctness and propriety of the designation have been often called in question, but its practical convenience has preserved it in use" [OED].