First, the obvious semiotic observation: just as we all (in the English speaking world) have agreed upon the word "semiotic" as the sound or symbol which refers to, or indeed signifies, the state of being only partially an idiot, so the word "hummus" is only an agreed (and less tasty) substitute for any substance which bears some base resemblance to a dippable blending of chickpeas, sesame, garlic, olive oil and lemon juice.
However, we can't stop there. The question then arises, at what point does the signifier cease to refer to the signified - is "hummus" still hummus if, for instance, it contains barely even one chickpea but instead quite a few broad beans? Moreover, is there a Platonic ideal for hummus, and if so can we get the recipe? Or are the Greeks still mad at us over that Marbles thing?
And even that isn't the full story. Let's look now at the etymology.
According to Wikipedia, the first recorded use of the word only goes back as far as 18th-century Damascus, which of course isn't even in Greece, and it was actually spelled like this: حُمُّص بطحينة (ḥummuṣ bi ṭaḥīna). In fact, "hummus" is only our closest approximation, and you'd have to ask someone from Turkey for decayed organic matter from the ground before you'd get what you were after (which indeed someone must have done because it was apparently from Turkish that the word first entered our language).
To go back further, though, requires that we turn to those masters of informed (but often mostly baseless) speculation: the historians. And, erm, recipe book writers, apparently: 12th century Egypt, says one food botherer. But slightly more believable is mention of a much nuttier variant, which also swapped vinegar for lemon juice, found in a 13th century Arab cookbook called Kitab Wasf al-Atima al-Mutada bi-Pukka by Djami al-Ivr.
Perhaps I was right, then, when I said "everything and nothing" - "hummus" is not entirely hummus, yet what is hummus anyway, and is its history (or lack thereof) not somehow visible in "hummus", if you look hard enough? - but at least now I know why. Even if I am suddenly a bit peckish...
(I really should have thought about that danger before I started this nonsense).
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On an almost completely different tangent, look at this:
I suppose one day people will wonder where so many of these things came from. Maybe they'll call themselves etsymologists.