1665–75; < French, equivalent to clair clear + voyant seeing (present participle of voir to see < Latin vidēre; see -ant)

Clairvoyant literally means “clear-sighted” in French, and for nearly 200 years that is what it meant in English as well. It wasn’t until the mid-19th century that it took on the meaning of “having psychic gifts” or “seeing beyond” that it carries today.
In the 19th century, the term clairvoyant was widely used in a medical context. An especially astute doctor might be able to see a patient’s symptoms and try to make a “clairvoyant diagnosis.” While some of these doctors were legitimate and extremely skilled, the term “clairvoyant physician” was generally used to describe your typical 19th-century quack. Occasionally, these people were brought to justice. The 39th Volume of The Journal of the American Medical Association contains an article about one such court case, from 1898, in which one can find this rant: “Whether the plaintiff calls herself a medical clairvoyant, or a clairvoyant physician…matters little…it was held that she was not entitled to recover for her services, she having no license to practice medicine.”
As the meaning of clairvoyant started to shift, reference books of the time attempted to approximate the new uses of the word. The 1873 edition of The American Cyclopaedia describes a clairvoyant as someone who can see through opaque objects, therefore possessing the power to “read a book unopened, or a letter which is enclosed in a solid wood box.” Today, however, clairvoyant carries more spiritual connotations, and such skills would never be cheapened by freak-show displays like divining the text of an unopened book. Rather, the modern clairvoyant prefers only to “see” things that cannot be easily refuted by disbelieving skeptics.

— The Clairvoyant: A 1934 film starring Claude Rains and Fay Wray.
— The Clairvoyant Journals: A conceptual art piece (1978) by poet Hannah Weiner. It was written in the form of a diary with 3 concurrent and contrasting voices narrating, and was performed live.
—“The Clairvoyant”: A 1988 song by the band Iron Maiden, purportedly inspired by the death of British psychic Doris Stokes.