Our word marriage goes back to the Romans, who used the word maritus (of unknown origin) to refer to a married man. Marriage was very different in ancient Roman society. In earliest times, a Roman woman had very few rights; she was under complete control of her father or her husband her entire life. She could only marry with her father's legal consent. Marriage was thought of as a legal institution created for the purpose of having children. There were two types of marriage: cum manu, in which the wife was basically enslaved to the husband, and sine manu, in which the wife remained basically enslaved to her father. Under cum manu, a wife could hold no property, and had essentially the same rights as a daughter of the family (except that her husband could not kill her or sell her, as he could his daughters). Divorce was not difficult, and required little special legal or religious recognition, although it was rare, since the woman would have been left destitute. I am not making this up.
This kind of incredible misogynism is rare among ancient societies, and tended only to exist when one tribe militarily destroyed another (also extremely rare), and enslaved its women. There is no evidence that this is actually how the customs arose in ancient Rome, but the historical record is spotty enough that such an event could have easily been forgotten. In any event it is not beyond the realm of possibility that maritus is derived from the name of Mars, the Roman god of war.
Over time the Romans relaxed their ideas of marriage. By 100 BC, the rights of a woman in marriage were much greater — she could own her own property, and could enter into legal agreements without her husband or father's explicit consent. In fact, by the time of Augustus and Jesus, the institution of marriage had weakened considerably in pagan Rome — divorce, remarriage, adultery, and children outside of wedlock had become quite common, especially among the upper classes, and the emperor Augustus felt it necessary to impose harsh penalties on those who broke their marriage vows. By this time maritus had given rise to the verb maritare, "to marry".
The Germanic tribes who invaded southern Europe, toppled the Roman Empire, and borrowed many words from Latin (including maritare, taken into Old French as marier, and then into English as marry) had a view of marriage similar to many conservative people today: they were strictly monogamous (remarriage and divorce were unknown), avoided sexual activity before marriage, punished adultery and promiscuity severely (particularly the females), and so on. It's extremely interesting to me that these ancient Germanic attitudes, planted in western civilization almost two thousand years ago, have persisted so long, and are now so closely associated with conservative Christianity, despite their pagan origin.
In modern western society, the concept of marriage is undergoing the most profound change it's ever seen. A marriage between a man and a woman who considered themselves equals would have been difficult for a Roman or ancient German to conceive of; and marriage between two men or two women would have been beyond belief. (Homosexual relationships were indeed permitted socially, but never considered 'marriage'.) Western culture often congratulates itself on its technological prowess, its medical advances, and its political freedom, but to my mind, this shift in attitude — this expansion of the idea of marriage to one of equal partnership between any two people — is one of the greatest contributions of modern society to human life and love.