Each language is a namespace, whether it is a natural (ethnic) language, a constructed language, the technical terminology of a profession, a dialect, a sociolect, or an artificial language (e.g. a programming language). Some modern programming languages such as C++ or Java can handle multiple namespaces within the language.
Examples: Within the limited world of your family, you might be known as "Charlie". Within a larger group of strangers, the name "Charlie" might not be unique, so you are instead "Charlie Brown, 17 Main Street". In (the namespace of) some other family, the name "Charlie" might refer to a different person than you.