What is the origin of the idiom "a sight for sore eyes" and when to use it?

The origin of the idiom "a sight for sore eyes" is believed to date back to the 17th century and is used to refer to a person or thing that is especially attractive, pleasing, or beautiful to look at, despite being unusual, different, or contrasting with typical standards of appearance. It suggests that the person or thing stands out and brings a sense of relief or delight to the observer's eyes, even if they may be unconventional or unexpected in their visual appeal.