As far as dilapidated meaning "stone", my dissecting of it brings me to "completely throw stones" (French dis + lapidare). This is my core issue with which I'm dealing. For comprehension and vocabulary purposes, I want the kids to be able to come to this etymological meaning and merge it cognitively with the dictionary definition. I want them to begin moving toward doing this automatically when they read or take tests. My idea of calling it the "essential meaning" was to simplify the term, but still be as pedantic as possible. In other words, I'm all for isopaleocopric pedagogy.