What is the origin of the idiom "have a roving eye" and when to use it?

The phrase is thought to have originated in the 19th century, when it was used to describe sailors who were away from home for long periods of time and were therefore more likely to be attracted to other women. It is used to describe someone who has a tendency to look at or show interest in others, especially in a romantic or flirtatious way, despite being in a committed relationship.