After the initial couple of posts, I lost steam a bit. Didn't know what word to analyze.
Then I thought, how about steam? The mallu word for steam is ആവി; നീരാവി, to be really specific. ആവി is just vapor.
We also have the verb അവിയുക - to cook in steam, from which comes the name of our favorite mallu dish അവിയല്്.
ആവി also appears in the verb ആവിയെടുക്കുക, to feel hot or sweaty. I guess, it originally meant to feel "steamy".
Interestingly, ആവി in Tamil also means spirit or ghost. So നീരാവി could also be interpreted as the spirit of water!