The UK for one doesn't have the concept of a legal name. As an adult you can call yourself anything you like, as often as you like.
You can complete a deed poll document to change your name on official documents, but it doesn't 'make legal' your new name, it just officially states that your new name supercedes your old name.
“I [old name] of [your address] have given up my name [old name] and have adopted for all purposes the name [new name].
"If the individual changing their name so wishes, evidence of a change of name (forename and/or surname) may be provided by a procedure known as deed poll."
Actually, I guess it really must be a foreign key M{0,}:N as a many-to-many to allow for having multiple names.