The English word food is a past participle, though it can also be used as the simple past of the third person singular, or most other persons as well, come to think of it, English not being terribly big on conjugations.
The verb "to foo'" has a number of meanings, among them being the act of exclaiming with a very mild, euphemistic oath. So, for example, if one wished to foo, one could say, "Oh, foo!"
This may not be clear so here's a bit of example dialog showing this usage.
Dave walks in. "Hey, Sam, have we food?"
Sam: "Dunno. Not me, haven't food. Not at all, not all day. Ask Joe."
Dave: "Hey Joe, have we food?"
Log splitter: "GRRRRRR!"
Joe: "What? Speak up -- can't hardly hear you over the log splitter."
Dave: "Do we have any food?"
Joe: "What? What's that supposed to mean? Your grammar's all wrong."
Log splitter: "CRACK!!"
Dave: "You leave my grammar out of this!"
Joe: "I'm sorry, Dave. I'm afraid I can't do that."
Dave: "Why's she so special all of a sudden?"
Dave: "Who what?"
Joe: "Who's special?"
Dave: "What kind of question is that supposed to be?"
Joe: "A simple one."
Log splitter (still squeezing the now long-since-split log): "GRRRRRzzzzzzGRRRRRmpf PHOOOSHshshshshsh!"
Joe: "Well there's your answer, you done it yourself."
Dave: "Done what?"
Dave: "What about food?"
Joe: "Dave, you OK? You're talking like one 'o them old-time adventure games."
The following section, formerly described as a meaningless jumble of scratchings, has had a significant amount of entropy removed from it in an effort to produce hilarity, with what might be adjudged a somewhat mixed level of success.
The verb is believed to have descended from an ancient Tauareg word, used in North Africa in the 6th century BC, and thought to have been pronounced "Fooey". Possible examples have been found in several manuscripts of the Ethiopic translation of the Book of Enoch, though the mold which inevitably grows on a parchment manuscript after it's been stored in a hole in a tree in a rainforest for 2300 years has made it difficult to be entirely sure. This, in turn, has led to speculation that the word may have originated as an expletive used by Enoch himself, possibly upon encountering that herd of celestial cows which first appear in chapter 86 of his (rather long) book.
The path taken by Fooey once the Tauregs learned it from Enoch is less clear, but it may have jumped the Sicilian Channel and then swum across the maelstrom to arrive in southern Italy some time around 300 BC, where it entered the Etruscan language. Evidence for this consists of an image discovered on the inside of an urn when a curator at the British Museum dropped it. When he'd stopped yelling about his bruised toe and started to sweep up the pieces of the former urn, he noticed that one of the bits was engraved with what could have been an "F". The fact that the "F" was found, upon further examination, to have been inscribed on the urn with a magic marker led, in turn, to the realization that the Etruscans had a far more technologically advanced society than anyone had realized, and has subsequently convinced a number[how many?] of scholars that there must have been a link between the Etruscan civilization and that of Atlantis.
Etruscia fell in the disastrous Romulan invasion of 273 BC, which culminated in the building of a new, heavily fortified capital which they named Rome, after which city the later Etruscan civilization was itself subsequently named. I was about to mention that the impetus for building the new city came from the very energetic Pope Remus, who in turn lent his name to some of the earliest myths about the city, but I realized that I've gotten rather far afield from the etymology of 'food' and decided not to.
Returning to the topic of the verb ... From Romania, whose ancient capital was Rome, the verb followed divergent paths, next surfacing in the court of Louis XVII as the previously mentioned word fooer, which is said to have been pronounced "Foo ... eh?", no doubt due to the influence of the Canadian diplomats who were so frequently seen at court.
The secondary path taken by the verb seems to have been via ancient Prussia, where it would have taken the form fooen (as we mentioned previously). However, the evidence for this is somewhat sparse, and in fact consists almost exclusively of an inscription found on the back of a photograph of Bismark standing next to a blimp marked with an Iron Cross which was found hidden in a bomb shelter in Hamburg after the war (no, not that war, that other war). Since the writing was in German, of course, the spelling was a bit wobbly, and an English speaker might have been forgiven for thinking that what was written on the photo was actually "Voom!".
The final fusion into the modern and useful English verb "Foo!" came with the Norman invasion, when Norman, who was known for his frequent but mild epithets, visited his brother Jules in his flat in London in the late summer of 1953.