aka = argha/arghya = aqua?

From: Marc Adler (marc.adler_at_gmail.com)
Date: 03/29/05 

Date: Tue, 29 Mar 2005 00:12:22 GMT

I'm reading (the?) "Hojoki" by Kamo no Chomei right now, and in the
description of his hut, he mentions setting up an "akadana" 閼伽棚,
which is a little set of shelves for water and flower offerings to the
Buddha. Akadana is glossed as aka + tana ("shelf" in Japanese), with an
explanation that "aka" comes from the Sanskrit word for water.

Kojien (the standard big Japanese dictionary) has "argha; arghya" as the
Sanskrit for "aka" here, indicating that it is mainly used as a word for
the water offering.

あか【閼伽】
〔仏〕(梵語argha; arghya) 貴賓または仏前に供えるもの。特に水をいう。ま
た、それを入れる容器。

So, my questions: What is the Sanskrit word for water (there are two
versions in the dictionary entry), and is it a cognate of Latin aqua?

Thanks,
Marc