What is the origin of the idiom "kiss of death" and when to use it?

The origin of the idiom "kiss of death" is uncertain, but it is believed to have originated from Italian mafia culture, where a kiss on the cheek was given to someone who was marked for death. This phrase is often used to describe situations where a particular action or event will have negative consequences, such as a politician receiving the endorsement of an unpopular figure or an actor being cast in a string of unsuccessful films. It can also be used in personal situations, such as when someone makes a decision that will have serious negative consequences for their career or relationships.