Xian semantically developed from meaning spiritual "immortality; enlightenment", to physical "immortality; longevity" involving methods such as alchemy, breath meditation, and T'ai chi ch'uan, and eventually to legendary and figurative "immortality".
The xian archetype is described by Victor H. Mair.
They are immune to heat and cold, untouched by the elements, and can fly, mounting upward with a fluttering motion. They dwell apart from the chaotic world of man, subsist on air and dew, are not anxious like ordinary people, and have the smooth skin and innocent faces of children. The transcendents live an effortless existence that is best described as spontaneous. They recall the ancient Indian ascetics and holy men known as ṛṣi who possessed similar traits.1994:376
According to the Digital Dictionary of Buddhism, Chinese xian (仙) can mean Sanskrit ṛṣi (Rishi "inspired sage in the Vedas").
The word xian
The most famous Chinese compound of xiān is Bāxiān (八仙 "the Eight Immortals"). Other common words include xiānrén (仙人 sennin in Japanese, "immortal person; transcendent", see Xiānrén Dòng), xiānrénzhăng (仙人掌 "immortal's palm; cactus"), xiānnǚ (仙女 "immortal woman; female celestial; angel"), and shénxiān (神仙 "gods and immortals; divine immortal"). Besides humans, xiān can also refer to supernatural animals. The mythological húlijīng 狐狸精 (lit. "fox spirit") "fox fairy; vixen; witch; enchantress" has an alternate name of húxiān 狐仙 (lit. "fox immortal").
The etymology of xiān remains uncertain. The circa 200 CE Shiming, a Chinese dictionary that provided word-pun "etymologies", defines xiān (仙) as "to get old and not die," and explains it as someone who qiān (遷 "moves into") the mountains."
Edward H. Schafer (1966:204) defined xian as "transcendent, sylph (a being who, through alchemical, gymnastic and other disciplines, has achieved a refined and perhaps immortal body, able to fly like a bird beyond the trammels of the base material world into the realms of aether, and nourish himself on air and dew.)" Schafer noted xian was cognate to xian 䙴 "soar up", qian 遷 "remove", and xianxian 僊僊 "a flapping dance movement"; and compared Chinese yuren 羽人 "feathered man; xian" with English peri "a fairy or supernatural being in Persian mythology" (Persian pari from par "feather; wing").
Two linguistic hypotheses for the etymology of xian involve the Arabic language and Sino-Tibetan languages. wu and Davis (1935:224) suggested the source was jinn, or jinni "genie" (from Arabic جني jinnī). "The marvelous powers of the Hsien are so like those of the jinni of the Arabian Nights that one wonders whether the Arabic word, jinn, may not be derived from the Chinese Hsien." Axel Schuessler's etymological dictionary (2007:527) suggests a Sino-Tibetan connection between xiān (Old Chinese *san or *sen) "'An immortal' … men and women who attain supernatural abilities; after death they become immortals and deities who can fly through the air" and Tibetan gšen < g-syen "shaman, one who has supernatural abilities, incl[uding] travel through the air".
The character and its variants
The word xiān is written with three characters 僊, 仙, or 仚, which combine the logographic "radical" rén (人 or 亻 "person; human") with two "phonetic" elements (see Chinese character classification). The oldest recorded xiān character 僊 has a xiān ("rise up; ascend") phonetic supposedly because immortals could "ascend into the heavens". (Compare qiān 遷 "move; transfer; change" combining this phonetic and the motion radical.) The usual modern xiān character 仙, and its rare variant 仚, have a shān (山 "mountain") phonetic. For a character analysis, Schipper (1993:164) interprets "'the human being of the mountain,' or alternatively, 'human mountain.' The two explanations are appropriate to these beings: they haunt the holy mountains, while also embodying nature."
The Shijing (220/3) contains the oldest occurrence of the character 僊, reduplicated as xiānxiān (僊僊 "dance lightly; hop about; jump around"), and rhymed with qiān (遷). "But when they have drunk too much, Their deportment becomes light and frivolous—They leave their seats, and [遷] go elsewhere, They keep [僊僊] dancing and capering." (tr. James Legge) Needham and Wang (1956:134) suggest xian was cognate with wu 巫 "shamanic" dancing. Paper (1995:55) writes, "the function of the term xian in a line describing dancing may be to denote the height of the leaps. Since, "to live for a long time" has no etymological relation to xian, it may be a later accretion."
The 121 CE Shuowen Jiezi, the first important dictionary of Chinese characters, does not enter 仙 except in the definition for 偓佺 (Wo Quan "name of an ancient immortal"). It defines 僊 as "live long and move away" and 仚 as "appearance of a person on a mountaintop".