The Japanese word Nyorai (如来 thusly come?) is the translation of the Sanskrit and Pali word Tathagata, the term the historical Buddha used most often to refer to himself. Among his Japanese honorifics, it is the one expressing the highest degree of respect. Although originally applied only to Buddha himself, with the advent of Mahayana Buddhism Tathāgata (and therefore Nyorai) came to be used for all those who have achieved enlightenment, entities which occupy the highest of the four ranks of the Japanese Buddhist pantheon. Their rank is accordingly called the Nyorai-bu (如来部?, or Nyorai category).
The Buddhist honorific Nyorai is the Japanese translation of Tathāgata, a Sanskrit and Pali compound word whose exact meaning is uncertain. It was widely used in Indian religions other than Brahmanism as a term of respect for religious figures of exceptional stature, but it ended up being used only by Buddhism. Sanskrit grammar offers two possibilities for breaking up the compound: either tathā (thusly) and āgata (come) or tathā (thusly) and gata (gone), and Buddhist commentaries offer as many as eight different interpretations of its meaning. The most widely accepted is “one who has thus (tathā) gone (gata)” or “one who has thus (tathā) come (āgata)”, signifying that Buddha himself was no more than one in a long series of persons in the past and future to achieve enlightenment, and teach others how to do the same.