Bee's knees is a saying that your the best. Most wanted or highly desired.
I belive it's because if you look at a bee's knees, you notice all the pollen collected there? Farmers like pollen because it allows fruit and crops to grow... '
So, if a farmer said you were the "bee's Knee's" your as good as pollen...
Draw your own rational for it....
BTW, you think Fuck is a swear word? Nope, it's slang for fuc, or plant. Yep, if you were a farmer, you would fuc your field, and grow a good crop... So it became fuc your wife, and raise some kids... and then has over time, become a swear word, and has a less desirable meaning. But there you go.
Here is another one.
Shit. (Means Ship High In Transport.) When ships where used to haul fertilizer, (Shit) they would sometimes fill up with methane gas and other nasty gases off the fertilizer... poop. So to keep the gas problem to a minimum, ship high in transport and let the gas escape, and the sailors live a fine life breathing sea air, not methane trapped below in the hold, so thick it would actually kill them. (Yep, methane is heavy. so it collects in low spots, and you can't live in a methane rich environment, not much oxygen to breathe there, so you die just like you were drowing in water.)
Damn, sometimes I feel like Bill Nye, the science guy.. LOL