Literally, "it is appointed unto men to die once" (i.e., only one time), which is an antidote for the notion of the transmigration of souls - IOW, leaving a body behind in one life, and the soul entering into a new body in a next life, continuously.
Originally Posted by partaker of Christ
Obviously, not each and every person meet that "appointment". You pointed out Elias and Enoch, and there have been those raised from the dead, whom have died more than once.
"A text without context is a pretext."