put someone out of his or her misery

1

Kill a wounded or suffering animal or person, as in When a horse breaks a leg, there is nothing to do but put it out of its misery. [Late 1700s]

2

End someone's feeling of suspense, as in Tell them who won the tournament; put them out of their misery. [c. 1920] Both usages employ put out of in the sense of “extricate” or “free from.”

Words nearby put someone out of his or her misery

put right, put someone away, put someone down, put someone in his or her place, put someone on, put someone out of his or her misery, put someone right, put someone through his or her paces, put someone up, put someone up to, put someone wise