māter + ἄρχειν

Matriarch was coined in English around 1606, modeled on 'patriarch' by substituting Latin māter (mother) for Greek patḗr (father). The word is a hybrid — Latin and Greek bolted together — and it is an invention, not an inheritance. No classical language had a word combining 'mother' and 'ruler.' This absence is itself significant. The Greeks and Romans who invented 'patriarch' did not need a female equivalent because they did not imagine female rule as a normal category.

The word initially described biblical and historical figures: Sarah as the matriarch of the Hebrew people. By the nineteenth century, it expanded to describe any powerful older woman at the head of a family — the grandmother who ran the household, the widow who controlled the estate, the grandmother whose approval everyone sought. The word carried authority but rarely political power. A matriarch ruled a family. A patriarch ruled a family and a state.

Anthropological 'matriarchy' — a society ruled by women — is largely theoretical. No well-documented human society has been a true matriarchy in the sense of female political domination. Matrilineal societies (descent traced through the mother) and matrilocal societies (couples live with the wife's family) exist and are well-studied — the Minangkabau of West Sumatra, the Mosuo of China, the Khasi of Meghalaya. But matrilineal is not matriarchal. Tracing descent through mothers and being ruled by mothers are different things.

The word has gained cultural currency as the image of the powerful grandmother. Toni Morrison is called a matriarch of American literature. Oprah Winfrey is called a matriarch of media. The word now names cultural authority more than political power — influence rather than rule. The Greek árkhein (to rule) has softened. The mother's authority, in the word's modern usage, is earned rather than inherited and moral rather than legal.