fish-eating grin

The idiom "fish-eating grin" is a variation of the more commonly used idiom "cat-eating grin." Both idioms describe a specific type of smile or facial expression that reflects self-satisfaction, smugness, or deviousness. The origin of this idiom is unclear, with no definitive source or etymology found.

When someone has a "fish-eating grin," they are expressing satisfaction or amusement at the expense of others. It can be seen as gloating or reveling in one's own success or cleverness. This figurative usage of the idiom is more common than the literal interpretation.

Informally, the idiom is used in certain regions or cultural contexts to convey playfulness or mischievousness. It is often employed in a lighthearted or humorous manner, describing someone who is being sly or cunning in a situation or taking pleasure in someone else's misfortune.

The idiom "fish-eating grin" is associated with two other idioms: "crack a smile" and "fill one's face." When someone cracks a smile, they show a brief and often sudden smile. This idiom suggests that the person is letting go of their seriousness or reserve and allowing themselves to show some happiness or amusement. It is similar to the "fish-eating grin" in that it reflects a momentary expression of satisfaction or amusement.

On the other hand, "fill one's face" means to eat a lot or indulge in food. This idiom conveys a sense of excessive eating or consuming large quantities. While it may not be directly related to the "fish-eating grin," it adds to the understanding of the idiom's connotations of satisfaction and enjoyment.