I strongly suspect that Cheery originated from Pterry knowing Roz Kaveney and it starting a mental dialogue.

But, in my youthful ignorance, I thought it was tomboys (like me) objecting to being identified as male. I was three. Apparently I bit the hairdresser who referred to me as male.

Mind you, as soon as I finished The Truth, I turned to G and said "Do William and Sacharissa seem familiar to you?"