I thought it was simply that courgette is the french and zucchini is the italian. And since they're foreign, we, in our usual fashion, haven't given them an english name but simply stolen the foreign.

We had good attempt at anglicisation with 'egg plant' (which was the accepted term when I was young) but have now settled back to aubergine.

Do we have a preference for the french because we consider french cooking to be the best? And only use other languages for things that aren't traditionally french, I wonder? Pizza, paella, tapas etc.