My only source is having read Russian novels in English. I wonder if the "little" water is like someone's diminutive name, i.e., meant to show familiarity or affection. Like, Mishka is the diminutive of Mikhail.
I'd like to read more about the difference between living aqua and dead water.
The Hittite word, watar appears in a sentence that was the first clue that it was IE: nu ninda en e-iz-za-te-ni wa-a-tar-ma e-ku-ut-te-ni
Czech linguist Bedrich Hrozny translated this in early 1900 s as: now you will eat bread and drink water. After this breakthrough he was able to mostly decipher it. https://www.sjsu.edu/faculty/watkins/hittite.htm