More Stuff In My Head

I was reading about this guy who the writer said had made some very “inflammatory” statements. So, then this question started rattling around inside my head. Why is it that “inflammatory” means very “flammatory” and yet “insensitive” means not very "sensitive”? This, of course, led to a couple of other rattles. Do you have to “hearse” before you can “rehearse”? If you’re “disgruntled”, were you once “gruntled” or did you possibly have your “grunt” removed? Do you have to have a “course” before you can have a “discourse”? And if you didn’t like “discourse” could you choose ”datcourse”? Which leads one to ask…is the “pre” in “pretense” a “prefix”? Changes the meaning doesn’t it? Now it could mean the time before you were “tense”. With that in mind, what if you’ve been operating under “false pretenses”? Think about that for a minute. And what about this? You’ve got your mouse…mice thing…your goose…geese thing…what about the poor moose? Hmmm…