The dragon name Zennyo Ryūō is written with Japanesezen善 "good, goodness; virtuous", nyo女 "woman; female" or nyo如 "like; as if; be like; thus" (differentiated with the "mouth radical" 口), and ryūō龍王 or 竜王 "dragon king".
Zennyo is a common theme in Japanese art, usually depicted as a small dragon but sometimes as a human, either male or female, with a dragon's tail. The "female" representations could explain this variant character 女 (Visser 1913:162). Fowler (1997:155) cites Nishida Nagao 西田長男 that this 女 "woman" in Zennyo was an error for the original character 如. In Japanese Buddhist terminology,nyo 如 "like; thus" is used to translate Sanskrit words like nyorai 如来 "thus come" for tathāgata. Compare shinzennyo 近善女 "near goodness female" translating upāsikā "female disciple; female devotee".
Zennyo 善如 was also the name of a Jodo Shinshu priest (1333-1389 CE) who was a grandson of Kakunyo and the fourth chief priest of the Hongan-ji.
Some legends give the name of Zennyo as Zentatsu 善達 "goodness penetration" with tatsu達 "penetrate; arrive at; reach; realize" instead of nyo.
Zennyo or Zentatsu 善達 supposedly lived in the Ryūketsu 龍穴 "Dragon Hole/Cave" on Murōyama 室生山 "Mount Murō" in Nara Prefecture, which was an ancient locale of Japanese dragon worship and rainmaking ceremonies.
The oldest historical record is the 937 CE Ben’ichizan nenbun dosha sōjō 宀一山年分度者奏上 "Mount Murō Annual Report of Ordained Monks". It states that in 778 CE five Buddhist monks went to the mountain and ceremonially prayed for the health of futureEmperor Kammu (r. 781-806), who later established the Murō-ji Temple in appreciation. This text also states that in 781 CE, (Fowler 1997:147), "a Dragon King (龍王) who had been residing at this site vowed to protect the country and particularly the temple complex. For this gesture the dragon king was honored with a courtly rank, as was commonly offered to deities."
The ca. 1212-1215 CE Kojidan "Talks about Ancient Matters" specifies this dragon's name and history.
Mythological figure. As Ryo-o, a role in gigaku play. The character of the 'Dragon King' derives from the story of a Chinese king of the Northern Qi dynasty (AD 550-77) who was so handsome that he had to wear a fearful mask into battle so that his enemies would be terrified and his allies would not be distracted.
Some Japanese #Movember inspiration! This mask with a bristling moustache and beard was used for a Japanese courtly ritual dance which has survived in Japan since the Heian period (AD 794–1185). This is the mask for Ryō-ō, the Dragon King, a character who appears in a Chinese story from the Northern Qi dynasty (550–577). He was so handsome that he had to wear a fearful mask into battle so that his enemies would be terrified and his allies would not be distracted.