“The term ‘gender’ itself is problematic.
It was first used in a sense that was not simply about grammar by sexologists—the scientists of sex such as John Money in the 1950s and 1960s—who were involved in normalizing intersex infants. They used the term to mean the behavioral characteristics they considered most appropriate for persons of one or other biological sex. They applied the concept of gender when deciding upon the sex category in which those infants who did not have clear physical indications of one biological sex or another should be placed (Hausman, 1995). Their purpose was not progressive. These were conservative men who believed that there should be clear differences between the sexes and sought to create distinct sex categories through their projects of social engineering. Unfortunately, the term was adopted by some feminist theorists in the 1970s, and by the late 1970s was commonly used in academic feminism to indicate the difference between biological sex and those characteristics that derived from politics and not biology, which they called ‘gender’ (Haig, 2004).
Before the term ‘gender’ was adopted, the term more usually used to describe these socially constructed characteristics was ‘sex roles’. The word ‘role’ connotes a social construction and was not susceptible to the degeneration that has afflicted the term ‘gender’ and enabled it to be wielded so effectively by transgender activists. As the term ‘gender’ was adopted more extensively by feminists, its meaning was transformed to mean not just the socially constructed behaviour associated with biological sex, but the system of male power and women’s subjugation itself, which became known as the ‘gender hierarchy’ or ‘gender order’ (Connell, 2005; MacKinnon, 1989).”
— Sheila Jeffreys, Gender Hurts; 2014