Hi! You seem like the right person to ask: what is the word Silna uses that gets heard as “huk-kah-hoi” and translated as “disappear”?
This is something I've wondered too, so I'll give you my best speculations! As a non-fluent L2 speaker of Iñupiatun I'm limited in my knowledge and by my dictionaries, so if anyone wiser ever corrects or clarifies anything I say here, I'd be most grateful! Iñupiatun is not Natchiliŋmiutut!
The Terror scripts really saved me here. Note that when referencing the scripts, the Natchiliŋmiutut orthography therein is nonstandard; e.g. the Natchiliŋmiutut letter ř is rendered indistinguishable from r, š from s, and y and j are both used, perhaps interchangeably, etc.
The line is scripted:
LADY SILENCE (20) (CONT'D) If you do not leave now, you will disappear. Tarvauruq aulanngikkuvhi, huqaruirniaqtuhi.
The word is repeated in what I guess to be a Qikiqtaaluk dialect in the scripted line:
CROZIER (21) She says if we do not leave now, we are going to-- susqaruisinnarniaqtugut.
"We (plural) will disappear."
This was replaced onscreen with "huk-kah-hoi."
To correct Silna's scripted line as best I know (and to use the letter ŋ), it might be written:
Tařvauřuq aullaŋŋikkuvhi, huqaruirniaqtuhi.
With comparison, I believe that the single l in aullaq- "to depart/leave" and the second s in Crozier's line are typos (though may be mistaken); "suqaruisinnarniaqtugut" might be right, or the q may have been meant to be geminated: "suqqaruisinnarniaqtugut." Is there also a missing q in there? "Suqaruiqsinnarniaqtugut" maybe? I'm not sure, but there does seem to be a phonologically assimilated q in huqaruiq+niaq. Many postbases will drop a preceding consonant.
"Huk-kah-hoi" seems to correlate to huqaruiq- with a dropped final q (that is dropped due to Crozier not hearing it, rather than a postbase).
Hu(-) is a noun and verb stem and an interrogative pronoun meaning "what" or "to be what;" kina "who" is not in the 2023 Hadlari and Ikajuqtigiit Natchiliŋmiutut dictionary, which instead lists huna as "who;" it may not have the su/suna versus kiña "what vs. who" distinction that Iñupiatun does, but I can't find a handy source that explicitly states this.
The noun-to-verb postbase -qaq- means "to have/possess," and in Natchiliŋmiutut -qaq- can also mean "there is/there are." Therefore: huqaq- "to have what/something"/"to be there what/something/someone."
+ruiq- may be made from the +ruk- "to want/to crave/to feel the physical need for" postbase as seen in imirukpit "do you (sg.) want/need water," or it may be a form of the +huk- "to feel/experience" postbase that isn't cited on tuhaalaŋa.ca. If that r is actually an ř that's deleting the q, I don't know what it might be. And then the -iq- postbase means "to no longer," which sounds the same as in Iñupiatun piiq- "to vanish"/"to die" etc.
+niaq+tuhi is "you (plural) will (future tense)."
Huqaruirniaqtuhi "You all will no longer be."
