The one word students never want to see featured in any explanation of any kind, is 'arbitrary'. Yet those learning French come across it pretty much from the word go, because gender is.
'A moustache is feminine ?!!' I remember a female student exclaiming once during a lesson, looking at me with utter disbelief. Of course, I burst out laughing. Up until that point, such a seemingly obvious contradiction hadn’t occurred to me. French is my mother tongue and I know better than to spend any time agonising over the gender allocation of words.
‘A shirt for men is feminine (une chemise) and a blouse for women is masculine (un chemisier)’ was my answer. It’s also the example I quote the most, in order to encourage my students to let go and forego logical explanations, which amounts to squaring a circle and, crucially, distracts them from more important tasks, such as putting sentences together.
Gender, as it happens, can also be fluid in languages. ‘Après-midi’ (afternoon) can be both masculine and feminine. And so can the word ‘amour’ when used in the plural!
The word ‘automne’, which like its English counterpart ‘autumn’ comes from the latin ‘automnus’, is masculine in French. But, as I discovered a while ago, during most of the 19th century, its gender wasn’t fixed.
Some people would use the feminine, others the masculine, when talking about the harvest season. Somehow, it became masculine and was described rather poetically by the painter, Henri de Toulouse-Lautrec, as ‘Le printemps de l'hiver’ (winter’s spring).
Don't hesitate to send me your questions.