“Thus spake the Exalted One, thus spake the Perfect Arhat (as I have heard):
The world, Bhikshus, hath been fully understood by the Tathagata; from the world the Tathagata is set free.
The arising of the world, Bhikshus, hath been fully understood by the Tathagata; the arising of the world hath been put away by the Tathagata.
The ceasing of the world, Bhikshus, hath been fully understood by the Tathagata; the ceasing of the world hath been realized by the Tathagata.
The Way going to the ceasing of the world hath been fully understood by the Tathagata; the way leading to the ceasing of the world hath been practised (traversed) by the Tathagata.
Whatsoever in the world, Bhikshus, and in the world of the Devas, with its Maras and Brahmans, together with the host of recluses and brahmins – of devas and mankind — whatsoever hath been seen, heard, sensed, known, reached, sought after, traversed by the mind, insofar as all that hath been fully understood by the Tathagata, therefore is He called Tathagata.
Between that day, Bhikshus, on which a Tathagata fully understands the incomparable perfection of wisdom, and the day on which He passes away with that passing which leaves no basis for rebirth behind* (during all that time) whatsoever He utters and specifies, all that is surely so and not otherwise. Therefore is He called Tathagata.
As a Tathagata speaks, so He does; as He does, so He speaks. Thus, since He does as He says, and says as He does, therefore is He called Tathagata.
In the world, together with the world of the Devas, with its Maras, its Brahmans, its recluses and brahmins, together with all the hosts of Devas and mankind, the Tathagata is all-conquering, unconquered by any, He is the All-seeing Controller. Therefore is He called Tathagata.”
Iti-vuttaka, § 112
(*) – The commentaries have derived the word in many ways, of which two may be mentioned, viz.: a) – Tatha-gato, thus gone; b) – tatha-agato, thus come (like other Buddhas).
(Some Sayings of the Buddha, according to the Pali Canon, translated from the Pali by F.L.Woodward, Oxford University Press, Madras, 1925).