Where Did The Phrase The Cat's Pajamas Come From?
As any cat owner will know, our feline friends tend to be rather more discerning than their canine counterparts. All cats seem to have mastered a disdainful look, want only the finest things in life, and expect their humans to provide it for them. If cats wore pajamas, then, they'd almost certainly be luxurious silken ones.
The phrase "the cat's pajamas" has indeed come to mean something that's simply all-around great, but in a literal sense, it really means nothing at all because, well, cats don't wear pajamas. This curious quirk of the English language, it seems, dates back to around 100 years. Phrases reports that many unique animal-centric expressions originated with the 1920s flapper generation. The era was about positivity, creativity, and expressing your enthusiasm for things by deeming them "the monkey's eyebrows," "the snake's hips," and, yes, "the cat's pajamas." In context, this slang was easy enough to understand, even if there's absolutely no logical meaning to it at all.
The term may have come from excellent silk pajamas
Merriam-Webster states that this colorful phrase was first used in 1922. It's difficult to say why it continues to be in use over a century later, when similar compliments pertaining to the eyebrows of a monkey or the hips of a snake have seemingly vanished. The fact that the word "cat" was somewhat ubiquitous — often being used in the context of a "cool cat" — surely contributed to this.
Was there once a human "cool cat" famed for wearing excellent pajamas? History doesn't record that, but according to Mental Floss, the comic strip "Indoor Sports," from artist Tad Dorgan, employed the phrase and it entered common parlance from there.
Other potential origins of the phrase have also been suggested. Historically Speaking/Idiomation states that pajamas were just becoming popular over nightdresses during the 1920s, but that the phrase itself is much older. There's a suggestion that an English maker of pajamas, E. B. Katz, created wonderful silk ones in the 1800s and that "Katz's pajamas" were so renowned that King George III himself wore them. Whether there's any truth to this claim or not, it seems clear that groovy youngsters in the 1920s popularized the term.