The Tathagata Is Called the Arahant, the Perfectly Enlightened One.

At Savatthi. “Bhikkhus, there are these Four Noble Truths. What four? The noble truth of suffering … the noble truth of the way leading to the cessation of suffering. It is because he has fully awakened to these Four Noble Truths

as they really are that the Tathagata is called the Arahant, the Perfectly Enlightened One.

“Therefore, bhikkhus, an exertion should be made to understand: ‘This is suffering.’… An exertion should be made to understand: ‘This is the way leading to the cessation of suffering.’”

Sammāsambuddhasutta SN 56.23 https://suttacentral.net/sn56.23