Sorry, I know nothing beyond what the Mlotek's wrote and what appears on the other thread. However, it occurs to me that the Spanish connection should not necessarily be ruled out. If the Zeitlin-Secunda musical was set in the Sephardic community then a reference to Spanish, or perhaps Ladino, would have been appropriate, although according to the Mloteks the song was originally called "Dana Dana." The entire question may have simply been based on a transloators choice of a singable vowel.

There is undoubtedly material to be found about the original production in the YIVO archives, and that's probably where you would need to go (with a knowledge of Yiddish) to find out, unless you can get one of the Mloteks, or perhaps Hankus Nevsky, to provide some more information.

Have a zis'n pesach!

Benyomin ben Jaacov