Attested since 1922, of unclear origin. There are several suggested origins, but it may simply have been in imitation of the numerous animal related nonsense phrases popular in the 1920s such as the cat’s pyjamas, cat’s whiskers, cat’s meow, gnat’s elbow, monkey’s eyebrows etc. A popular folk etymology has the phrase referring to World Champion Charleston dancer Bee Jackson. Another suggestion is that the phrase is a corruption of business but this may be a back-formation. The singular bee’s knee is attested from the late 18th century meaning something small or insignificant in the phrase big as a bee’s knee. Also as weak as a bee’s knee is attested in Ireland (1870). It is possible that the bee’s knees is a deliberate inversion of this meaning, but is not attested.Today the phrase seem’s pretty common. I’ve heard t used on the 2003 film School of Rock with Jack Black. How common is it in 2018 is somewhat difficult to track. Five Thirty Eight‘s online tracker doesn’t have it as an option. Google’s Ngram Viewer only tracks until 2000, but is still a wonderful graph. Maybe the more important thing to be aware of isn’t how popular a phrase is (cat’s pajama’s was slightly more popular in 2000), but how cool you look when you use the phrase is probably more important. Unfortunately there’s no graph I can show some one for how cool they look when they use the phrase. If I could find a graph for that I’d be sure to share. When it comes down to it, though I really don’t know anyone who doesn’t like the phrase. This is probably because it’s predominantly used as a compliment. We could use a few more compliments in our daily discourse. So, have a go at it! Why not toss out “the bee’s knees” today in a conversation?
There’s a great post over at the Telegram about this phrase and other slang terms from the flapper era. Wiktionary gives us this background: