The name of the locality is attested in the forms Fontanetum, Fontanedum in 843 and in 846.
The toponym Fontenay comes from the Latin fontana, "source", suffixed from -etum designating a "set of fountains".
The complement le-Marmion alludes to the seigneury which belonged to a powerful family, the Marmions whose possessions extended across the Channel.
The gentile is Fontenaysien.
From 1829, on the initiative of Arcisse de Caumont, archaeological excavations were undertaken on the site of the Hogue tumulus with its sepulchral chambers dating from the Neolithic period. They made it possible to authenticate the presence of a population organized into a social group around 3600 BC. Another tumulus, that of La Hoguette, is visible about 600 meters away.
The parish of Fontenay was divided for the first time to form the parishes and seigneuries of Fontenay-le-Marmion and Fontenay-le-Tesson. The latter was again divided to form Saint-Martin-de-Fontenay and Saint-André-de-Fontenay (currently Saint-André-sur-Orne). The seigneury of Fontenay-le-Marmion then belonged to a powerful family, the Marmions whose possessions extended across the Channel.
