OP
I'm really sorry to hear that your son is being bullied like this. Children do this because whether in France or the UK - kids can be little sh*ts to each other the world over. Sorry to put it strongly like that, but my oldest son was bullied mercilessly at primary school - 6 years of that really knocked his confidence, and before anyone says anything I did go to the school, I did offer to move him (although by that stage he'd made friends in the year below so didn't want to). He really only got past it when he went to a completely different (and better) secondary school than the other boys in his year group.
He was bullied about a number of different things - first name, surname, his hair being curly - you name it the bullies used it.
Basically OP (and I expect you are feeling the same helplessness I did as I kept exhausting all official methods), nothing is probably going to help except him cultivating the 'I'm bored', 'Whatever' type persona that other posters have suggested.
I get the problem with his name in the part of France you are in, but if its not his name it will definitely be something else. They have decided to target him and changing his name is very unlikely to help.
Cultivating complete indifference to the bullies and making friends with other children somewhere else is the best thing. We also enrolled my son into learning a martial arts (which is still doing and is now the equivalent of a black belt) which helped with his confidence.
The school were cr*p and just didn't deal with it. In saying that I have seen other primary schools (moved my youngest son for different reasons to another one) deal with a boy who was being bullied spot on and nipped the issues in the bud. Likewise the secondary school both my two went to, dealt with Year 7 bullying of my eldest (it continued - 2 of the boys went from his old school and tried indoctrinating his new friends) and they squashed it completely once they knew.
So schools can deal with bullying it really depends on the outlook and culture of the school in question. Moving schools might be something to consider - my eldest didn't want to in the end, but at the end of the day he needs your love and support.
It does make my blood boil re bullies. We tried everything - in the end ignoring and complete indifference and making new friends was the only thing that helped my DS cope.
Good luck OP to you and Owen (which is a lovely name - one to be proud of).