1) alas it's a largely non-empty set, there are international treaties (one of them asking countris not to remove the last citizenship of someone) and UN branch

1) alas it's a largely non-empty set, there are international treaties (one of them asking countris not to remove the last citizenship of someone) and UN branches dedicated to the problem. I think currently it happens mostly in eastern Europe and Africa. At the personal level, loosing some papers, having registries burned during a war and being from a not really liked ethnic background might make your nationality hard to prove. There are systems trying to give "quickly" a nationality to a refugee. It is seen as a legal emergency. 2) the word was actually created as the opposite of "subject" (of the ruler), to insist on the democratic side, not as the opposite of "foreigner".