It's "derring-do" ... but it shouldn't be

I need help with these 3 phrases. I just can't figure it out... if anyone knows, please let me KNOW! Thanks! :)

1. Deeds of deeding-do
2. A tour de force
3. An idee fixe

1. deeds of daring-do -- I couldn't find this one so I'm guessing on the spelling, etc. I think it means brave deeds -- as in "tales of daring-do."
2. tour de force -- pronounced TOUR-de-FORCE, French phrase for "display of technical virtuosity; powerful exhibition of skill." (From "Le Mot Juste" edited by John Buchanon-Brown, 1980, 81, Vintage Books).
3. idee fixe (with one of those little marks over the first "e" in idee) pronounced EE-day FEEX, literally French for "fixed idea; obsession, preoccupation." From "Le Mot Juste."

"Derring-do" turns out to have an interesting history. It was a challenge to find, but the OED lists it as a "pseudo archaism" which originated with Chaucer, was misunderstood by Lydgate, picked up but misprinted by Spenser, and then taken up by Sir Walter Scott, and it's been "derring-do" ever since. The series of errors and misunderstandings have created a word meaning "reckless courage." If you have an OED, it's interesting reading.