Genki
Friends, I published a pretty detailed piece on the history of the word genki at Néojaponisme earlier this week. It's true that it relies mostly on one paper's worth of research, but matches my experience as a reader perfectly. (I ran across that example in Dōgen myself.)
Simon:
I can never disassociate the phrase "genki desu ka" from the (apparently pseudo-)gloss my Professor used to teach it: "Is your psychic stuff well-ordered?"