Sex: Comes from the Latin word ‘Sexus’ and has its root before that in Seco (period unknown) which meant ‘To divide in half’, consider also ‘secateurs’ and ‘section’. In Latin it was applied specifically to the division of the human race by gender.

It wasn’t used to mean intercourse until as recently as 1929 when D.H. Lawrence used the term ‘sexual intercourse’ meaning the meeting of two sexes, from then the term ‘sex’ has been used as shorthand.