If you were Anderson Cooper and you had been born in Germany, you wouldn’t be Anderson Cooper, because Germany is just one of a surprising number of countries with strict baby-naming rules and regulations. In some instances, as in Italy and Sweden, the motivation is humane—trying to spare the child embarrassment, ridicule and bullying in the increasingly wild and wooly international baby-name environment. In fact, some of these are not long-standing strictures, but relatively recent ones.
In Portugal, no nicknames are allowed on birth certificates, so Tomás would be OK, but not Tom. It’s also on the books there that children’s names must be traditionally Portuguese, a full name, and not unisex.