It's a slightly old-fashioned way to say someone looks good, but it's still used, especially in a playful or romantic context.
Here's a breakdown of why:
* Fetching originally meant "to attract or entice".
* Over time, it evolved to mean "attractive" or "pleasing to the eye".
* It's often used to describe someone's appearance, especially their style or clothing.
Think of it as a way to say, "You look great!" but with a touch of charm and a hint of flirtation.