桼: a lacquered knee

桼も表外漢字です。英語で、「varnish」です。
漆, lacquer.  It's liquid 氵, applies to/comes from wood 木, and can make a big nasty splash under your roof if you're careless.
膝, knee:  It's flesh so we get 肉 on the left.  Beyond that, I think of a wooden knee and water on the knee as things that can go wrong with it.

漆膝