Thanks for all the replies both on and off-list.
I am eager to hear any further input you might have on the nature of the nīvi/nīvī and related questions, but I would like to briefly zoom in on the word dhudhurikā.
Come to think of it, in the manuscript in which I found it, gha and dha can't be clearly distinguished. (Actually, from a purely graphic point of view they could, but the scribe does not seem to use the graphic peculiarities of the two akṣaras with a purpose.) Therefore the word might be either dhudhurikā or ghughurikā.
In this respect, in J.T. Platts' Urdū dictionary I see that the words ghagh[a]rā and ghagh[a]rī mean “a petticoat (= ghāghrā); a short frock” and that they should be related to the “S[anskrit] gharghara+kaḥ and gharghara+ikā” (p. 935 of the 2004 reprint). However, the meanings listed by Apte for ghargharaḥ, ghargharā and ghargharikā don't have much to do with "petticoat", see https://www.sanskrit-lexicon.uni-koeln.de/scans/AP90Scan/2014/web/webtc/servepdf.php?page=0477-a. (I might well be on a spectacularly wrong track.)
Does anybody have any thoughts on dhudhurikā/ghughurikā? Can anybody figure out which language it is?
the very best,