Rakan is an abbreviation of arakan 阿羅漢, which is the Japanese pronunciation of the Chinese transliteration of the Sanskrit arhat or Pali arahant, meaning "worthy one." Ōgu, literally "worthy" (ō 應) of "offerings" (gu 供), is the Sino-Japanese translation of arhat.
1. "Worthy one" (ōgu 應供, S. arhat) is an epithet of Buddha Shakamuni.
2. In the Abhidharma (commentarial and philosophical) literature that all Buddhists recognize as canonical, an arhat is defined technically as a fully ordained male who has successfully followed the Buddhist path to its conclusion, which is to say, a monk who will not be born again but is certain to enter nirvana when his current (final) rebirth comes to an end.
3. Any monk who is named in the sutras as an immediate disciple of Shakamuni Buddha. Mahayana sutra literature is famous for its disparagement of the arhats as disciples of the Buddha who are selfish because they strive for nirvana for themselves alone, whereas the noble bodhisattvas (the Mahayana ideal) vow to forswear nirvana and remain in the round of rebirth to alleviate the sufferings of all beings. Arhats are further depicted as ignorant of the emptiness (kū 空) of dharmas (hō 法), whereas bodhisattvas are said to be freed from suffering by their insight into emptiness even when their compassion takes them into the most painful realms of existence. In the Mahayana Buddhism of Song and Yuan dynasty China, nevertheless, the arhats were venerated as hermit sages who, in their eccentricities and supernatural powers, took on many of the qualities of Daoist immortals. The Zen school in medieval China was especially sympathetic to the arhats because it revered two of them, Makakasho and Anan, as the first and second ancestral teachers of the Zen lineage in India.
In any case, Chinese Buddhist modes of arhat depiction and worship have carried over into Japanese Zen, where they have survived from the Kamakura period (1185-1333) down to the present. Soto Zen monasteries and temples have a dedicated arhats hall, or at least an area near the central Sumeru altar, where images of the sixteen arhats (jūroku rakan 十六羅漢) are enshrined. The arhats are supplicated with regular offerings of food, drink, and merit. The morning sutra chanting performed every day includes a sutra chanting for arhats (ōgu fugin 應供諷經), in which they are asked to use their supernatural powers to liberate all living beings (i.e. to act as bodhisattvas); to support the monastic community both spiritually and materially (the latter by insuring a steady supply of food); and to prevent disasters. At Soto monasteries there is also a monthly offering to the arhats (rakan kuyō 羅漢供養) that is held in the arhats hall, and an elaborate arhats liturgy (rakan kōshiki 羅漢講式) that is held there semi-annually. ☞"arhats hall."