What is the origin of the idiom "love rat" and when to use it?

The phrase is thought to have originated in the United Kingdom in the early 20th century. Since rats are often associated with negative qualities such as sneaking around, betrayal, and spreading disease. By comparing someone to a rat, the term "love rat" emphasizes their disloyalty or infidelity in relationships. It is often used to describe men who cheat on their wives or girlfriends, but it can also be used to describe women who cheat on their husbands or boyfriends.