What is the origin of the idiom "have it in for someone" and when to use it?

The idiom "have it in for someone" is rooted in the idea of holding a grudge or bearing ill will against a specific person. While its exact historical origin is uncertain, it likely developed from the broader concept of personal or ongoing conflicts. It is used to describe instances where someone seems to have a persistent negative attitude or intention toward someone else, often resulting in antagonistic behavior or actions.