You can trace the etymology of English word rape to the Latin verb rapere, which literally means "to snatch, to grab, to take away". Legally speaking, this was related to the concept raptus - which meant kidnapping or abduction, and could include taking away a young woman from her family for elopement or other sexual purposes.

But did this really mean rape? The problem is that there were various concepts in the ancient world that included elements of what we consider rape, but did not map exactly onto our modern understanding of the word. So, for example, the Romans also had a concept of stuprum, which related to illicit sexual intercourse - which could, under certain circumstances, include what we would now call rape (i.e., sex without consent). But in its original meaning, it meant any act that brought shame or dishonour to a person (similar to the Greek notion of hybris), and could include adultery or sex with an unmarried women. Consent was not the crucial factor in defining such crimes - by definition, sex with slaves and prostitutes was not considered stuprum even if it was coerced - but rather had to do with the effects of an act on a person's reputation.

(See: Susan Deacy and Karen Pierce, eds., Rape in Antiquity: Sexual Violence in the Greek and Roman Worlds; Algeliki E. Laiou, Consent and Coercion to Sex and Marriage in Ancient and Medieval Societies; Amy Richlin, "Not before Homosexuality: The Materiality of the Cinaedus and the Roman Law against Love between Men," Journal of the History of Sexuality, 3 (1993): 523-573.)

Even in 18th-century America, the legal concept of rape did not correspond to modern-day understandings. As Sharon Block has shown, it was assumed at this time that all sexual intercourse involved a degree of violence and coercion, and therefore the concept of consent was not especially relevant to the prosecution of rape cases. What really mattered was the social status of the men involved, so upper-class white men were rarely charged with rape, whereas black men who had sex with white women were generally assumed to have been rapists.

(See: Block, Rape and Sexual Power in Early America.)

Today's understanding of rape was shaped to a large degree by second-wave feminist activism, perhaps best expressed by Susan Brownmiller's landmark 1975 book Against Our Will, which defined rape as "a conscious process of intimidation by which all men keep all women in a state of fear," and which made the oft-repeated observation that "rape is a crime not of lust, but of violence and power."

Brownmiller's book helped change attitudes toward rape, as well the legal framework of sexual assault. At the time it was published, married women could not charge their husbands with rape, and rape victims were required to provide a witness corroborating their story. Since the 1970s, many of these laws relating to sexual assault have been revised.

So some aspects of rape have a very long history (for example, the 130th law of the Code of Hammurabi stipulates, "If a man has ravished another's betrothed wife, who is a virgin, while still living in her father's house, and has been caught in the act, that man shall be put to death; the woman shall go free"), but the modern understanding of the word has its roots in the 20th century.