The (perfectly proper) phrase "Split the atom" has this unusual property: It expressly contradicts the original-language meaning of the term "atom." "Atom" comes from "a-" (not) and "tom" (from the greek "cut," as in "appendectomy"). "Split the atom" thus means "split the thing that can't be split."

Are there other terms that fit this mold? Please make sure that you have your etymology right before posting examples. Best of all would be linking in your comment to a dictionary that notes the etymology.