Until the late 1400s the word 'girl' just meant a child of either sex. If you had to differentiate between them, male children were referred to as 'knave girls' and females were 'gay girls'. Equally, a boy could be called a 'knave child' and a girl a 'maiden child'.

The word 'boy' also didn't used to mean ‘boy’ in the modern sense but ‘servant’. The word 'boy' meaning ‘young man’ probably derived from the way the 'servant' meaning was used as a pejorative term. It doesn't occur before 1440 so before then if you wanted to talk about a boy you called them a ‘girl’.

The ‘pink for a girl, blue for a boy’ coding is actually the opposite of the system that prevailed until quite recently. Until the 20th century toddlers of either sex were normally dressed in white, but when colours were used, boys were dressed in pink. At the turn of the 20th century, Dressmaker Magazine wrote: 'The preferred colour to dress young boys in is pink. Blue is reserved for girls as it is considered paler, and the more dainty of the two colours, and pink is thought to be stronger (akin to red).' As late as 1927, Time magazine reported that Princess Astrid of Belgium had been caught out when she gave birth to a girl, because 'The cradle…had been optimistically outfitted in pink, the colour for boys.'