Wikipedia
The Japanese term sennin is a loanword from Middle Chinese SenNyin 仙人 "immortal person", known also as xian "immortal; transcendent; genie; mage; djinn; sage; hermit" in Daoism.
Sennin is a common Japanese character name. For example, Ikkaku Sennin (一角仙人 "One-horned Immortal") was a Noh play by Komparu Zenchiku (金春禅竹, 1405–1471). The Japanese legend of Gama Sennin (蝦蟇仙人 "Toad Immortal") is based upon Chinese Liu Hai, a fabled 10th-century alchemist who learned the secret of immortality from the Chan Chu ("Three-legged Money Toad").
Usage examples of "sennin".
It was said to be in the Eastern Ocean, and people of extraordinary long lives, called Sennin, were supposed to dwell there.
The sennin could take no blame from Sun Hsiung and the female could return with honor to the areas for which she was best suited: the tea ceremony and, perhaps, flower arranging.
For his part, the sennin despised her on sight and silently cursed her former sensei for evoking his right of privilege here.