First of all, I wonder if thjuster(nesse) 'darkness' ↔ finsternis 'darkness', with thu ↔ Fin. The word can be understood as in metaphorical darkness (non-good or land of the dead), but may also refer to the astro-geographical understanding of Fennoscandia, Ódáinsakr/Odenma/Uttarakuru as polar country where there is little sunlight. For example see Uttarakuru's polar axial line, or "mountain", Meru (alternative spellings include Sumeru, Sineru and Neru) here and the darkness description here. In this context the darkness-dwellers would refer to persons living in country that has actual Nordic seasons of light summer nights and dark winter days.'Tsjoed' in (modern) Frisian means 'wrong', 'bad', 'evil'.
On the Tschuden/Chuds wiki: (German): "Die mündliche Überlieferung der Samen und nördlichen Karelier ist reich an Geschichten über als Tschuden bezeichnete Räuber und Feinde" (translated: "Oral tradition of the Sami and northern Karelians abounds with stories of robbers and enemies known as Chuds") // (English): "another hypothesis contends that it is derived from the Sami word tshudde or čuđđe, meaning an enemy or adversary"
THJONSTER is 'sorceress' and THJUSTER(NESSE) is 'dark(ness)', mostly used in negative context.
Overwijn (1941, pp. xxxviii-ix) refers to Tsjoedi/Tsjoegi/Tsoegi => tsigoe, tsigeu => Tsigane, Tsigoin, Zigeun(er); i.e. 'gypsy'. Overwijn (1951, p. 90c) "de verzamelnaam voor Finnen, Letten, Esthen en Lappen in het Russisch is: Tsjoedskïï" van "Tsjodis of Tsjoedis".
The issue of the word is not of small importance, for linguistical substituting of Sumerian cu/su/suen ↔ Germanic Finn (in Finnish: Suomi, suomalainen) forms a central part of evidence for OL narrative's archaic roots (this extends also to associated Norse saga lores). More about that here. There are clues to the extreme age of the word, way beyond the 2000 BC Frisian-Finnish context in OL.
The Bock family saga story of Sven, Dan and Fin (the last also called Lemminkäinen or Balder, of the Aser house) emerging out of the icy prison of Altlandis 'all-land-ice' with cattle and other household animals is paralleled by the Norse story of first Æsir man Búri-Finn emerging out of ice, again with a cattle story related to it (the latter Finn name to Búri is given in the Frá Fornjóti narrative and is given in compound form Puzur-Suen in Sumerian King List). Compared next to Bock family saga and OL narratives, the Norse version seemingly confuses the late ice age Altlandis story with the later 4.2 kiloyear event Aldland story as given in the OL, perhaps due to Finland's Aser Odenma name similarity to Æsir Oden/Odin or Wodin.
That the name referred originally to the late ice situation is supported by the fact that the Greek Atlas of Atlantis was known to Egyptians as Shu – the same root word again. Furthermore, his attributes of lion, peace and air and wind are the same attributes of Fin or Lemminkäinen of Bock family saga who turns in elder days to role of Ukko, symbolized by lion, peace and sky (the OL narrative Finns are far more warlike).
And now comes the final, most spectacular part: the same story was known to American Indians. Just as the Finnish and Norse versions were about the Finn or Suomi people living inside the ice in Hel (there is chronological evidence for mammoths living inside the Nordic ice walls, see the Herttoniemi mammoth here), so did the American Indian version also know, accurately, of living on an unfrozen land at the end of the last ice age. Name of that American Indian tribe? Heiltsuk, or 'Hel-Tchudes'. The same exact core word, again underlining the archaic age for the term.
The Bock family saga says that after the ice melted the Aser and Asynjor sent men all over the planet as white emissaries, these being called Han Udens Man or 'He-Sun's-man'. I have no evidence of these early continent-hopping travels, other to note that as per the Mongol histories in the early 1200s the Genghis Khan lost a battle to distant northern Eurasian Narayrgen 'Men-of-the-sun', the exact same name used in similar geographical context. Thus it's unknown if the story and the name-word was taken from Europe to Americas or is a generic, planetary-wide term by no means limited to European alone. Nonetheless the American story is backed geologically. See more about that kind of old late ice age stories here.