trance (n.)

late 14c., traunce, "swoon, fit of fainting from extreme dread or suspense," also "half-conscious or insensible condition" from illness or injury, also "ecstatic state of insensibility to mundane things, state in which the soul seems to have passed from the body into another state of being;" from Old French transe, Anglo-French trauns, trance, "crossing" of a sea; "coma; passage from life to death; fear of coming evil" (12c.). The general notion is "a passage away or apart."

This is a verbal noun from transir "die, pass on" (also "be numb with fear"), from Latin transeo, transire "go across or over, pass over, hasten over," from trans "across, beyond" (see trans-) + ire "to go" (from PIE root *ei- "to go").

The Latin verb had the many (and not always compatible) figurative extensions typical of verbs for "go across, pass over": "go over to the other party or opinion," "be changed or transformed," "pervade," "excel," "transgress," "summarize," "leave untouched," also "pass away, cease to live, die" (perhaps euphemistic; compare obituary).

French trance in its modern sense is said to have been reborrowed from English. As a music genre, by c. 1993.