[Ngdyoysv]

Buddhadasa Bhikkhu goes into it at great length in his essay "Two Kinds of Language". You can find it on the net. Bhikkhi Bodhi mentions it in the introduction of his re-work of Nanamoli's translation of the Majjhima Nikaya. You can see Thanisssaro talking about it in his book Wings to Awakening, which is also available on the net. All agree that the Buddha co-opted these terms and gave them his own meanings in his own teachings. It is not a matter of conjecture.

There are certain teachings the Buddha gave which are absolutely consistent internally and externally, that is, within their own system of thought and also comporting with reality as it is and as we can all see for ourselves here and now. The Buddha also proclaims in many places in the discourses that his own teachings are timeless, applicable to everyone, and visible to anyone here and now. A person who reads and studies the suttas critically and carefully can quickly come to recognize what the Buddha taught, what might be suspect, and what is complete hogwash. The Buddha states in several places what his own teachings are, and distinguishes them from the teachings of others, and why. It is not that difficult to separate the wheat from the chaff.