The cat’s pajamas

Meaning: Someone or something that’s really awesome.

The phrase sprung up in the 1920s in the United States. At this time it was “hip” to combine an animal and a body part or clothing to call something cool, such as “the bee’s knees,” and “the caterpillar’s kimono.” Specifically, ‘flapper girls’ of the decade were often called ‘cats,’ and pajamas were gaining popularity. So, there ya go.