chametz

The word chametz (or hametz) derives from the root חמץ - meaning "to be sour, to ferment, to be leavened". Jastrow claims that perhaps the original meaning was "to be hot", which led to another meaning - the color red. Jastrow gives the example from Moed Katan 23a, where they mention בחימוצתא רומיתא סומקתא - which he translates as "Roman dyed red garments".

Other words that derive from the same root חמץ include hometz (or chometz) חומץ - vinegar, and its derivative humtza חומצה - acid. One example of hometz in the Tanach is in Megilat Rut (2:14), where Boaz tells Rut to: וְטָבַלְתְּ פִּתֵּךְ, בַּחֹמֶץ - "dip your bread in the vinegar". This sounds like an unusual dip for bread, and the Daat Mikra suggests that perhaps hometz here meant sour milk.

I have heard however a different explanation that has more linguistic significance. The Arabic term for chickpea dip - commonly known in English as hummus - has the same root as hometz - חמץ. In the Talmud, there is reference to a legume known as himtza חימצא (or חימצי). So perhaps Boaz was suggesting something a little more tasty - bread with hummus.

Does himtza also derive from the same root as chametz? Klein says that it probably does. I'm not 100% sure - in Aramaic chametz is chamiya חמיעא. Horowitz (p. 108) teaches that the letter tsade is a "triplet letter" - having once had three different pronunciations. Aramaic acts as a mirror into the original Hebrew pronunciation. He points out that sometimes Aramaic preserves the current sound of tzade - צרח is the same in Hebrew and in Aramaic. Occasionally tsade has the sound of tet - נצר in Hebrew is נטר in Aramaic. And then there are cases where tsade is like ayin - ארץ in Hebrew is ארעא in Aramaic. So while the Aramaic word himtza חימצא preserves the tzade, chamiya חמיעא - has it replaced with an ayin. This could very well point to different origins.