Meaning
Excellent - the highest quality.
Origin
It's difficult to know if we need an etymologist or an entomologist for this one.
Bees carry pollen back to the hive in sacs on their legs. It is tempting to explain this phrase as alluding to the concentrated goodness to be found around a bee's knee.
** Here at The Bees Knees, I strive to provide excellent and top quality products, as well as excellent customer service! I <3 my clients, and if you are searching for an item let me know and I will try my best to find it for you!