fubar is slang (mangled german) for the word "furchtbar" which means terrible or horrible -- think of it as the opposite of "wunderbar." furcht means fear, literally translated, and the "bar" is added to make it an adverb or noun, as the case may be. notice that "wunderbar" translates literally into wonderful. by contrast, you should treat furchtbar as an idiom and translate it to mean terrible or horrible.
by the time our troops landed at omaha beach, d-day (june 6, 1944), the term fubar had undergone a pejoration. the soldiers in saving private ryan were probably contemplating the pejorative, anglicized acronym "fubar" which they would translate as "fucked up beyond all recognition."