Smalltalk is often considered to be the purest OO language, and predates C++, Java, and C#. It didn't use keywords to control access, but used a basic policy. Smalltalkers would say that fields were private and methods were public.
However the private fields don't really mean the same as what they mean in C++ based languages. In C++ et al aaccess is thought of as textual scope. Consider an example with a class Programmer which is a subclass of class Person with two instances: Martin and Kent. In C++ since both instances are of the same class then Martin has access to the private features of Kent. In Smalltalk's world view access is based on objects, so since Martin and Kent are different objects Martin has no business getting at Kent's fields. But again, since everything is object based Martin can get at all his fields even if they were declared in the Person class. So data in Smalltalk is closer to protected than private, although the object scope makes things different in any case.
Lots more good stuff, especially for those of you working in a mixed language paradigm - I expect that it would be very easy to have misunderstandings based on simple misconceptions of these terms across languages
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