What is the origin of the idiom "make sheep's eyes at someone" and when to use it?

The idiom "make sheep's eyes at someone" originates from the behavior of sheep. Sheep are known for their innocent and gentle nature, and when they are attracted to another sheep, they often gaze at them with soft, tender eyes. This behavior inspired the idiom, which was first recorded in the English language in the late 18th century. It is used to describe the act of giving someone a look of affection, adoration, or romantic interest. It suggests subtle expressions of romantic interest, typically in a lighthearted or playful manner.