Gender

https://thecollegefix.com/evolutionary-biologist-forced-out-of-academia-for-insisting-male-and-female-are-not-social-constructs

The terms sex and gender have been considered to be interchangeable in English until the last few years. https://www.southwesttimes.com/2013/01/sex-vs-gender-are-the-two-interchangeable/

The English word gender was originally just a polite alternative to the use of the word sex as a noun. The first use of gender in this sense is from the 15th century.

Thus historically in English gender and sex were synonyms. Feminists and others have now successfully changed the language to the point that sex and gender are now considered to be entirely separate and many people don't realise that was ever otherwise. The first attestation of gender being used in this sense was 1963.