They used to be very strict with first names here but it looks like that's no longer the case.
Although, it depended on community to community.
When my father went to the city council to register our birth, the plan was to name me "Els", which is a fairly common first name here (no longer in fashion, though).
Reply: "Els is the name of a tree. It has to be Elisabeth"
Since my last name is a long one, my dad opted for a slightly shorter first name.
But now, you can name your child Duoduo?