Topic: Dushgoi, Morgul and Dol Guldur
In the search for etymology for words in Dictionary, I've found following connections between Black Speech word "dushgoi" and Sindarin compound words "Morgul" and "Guldur":
1) "Dushgoi" is the BS name for "Minas Morgul" mentioned in "The War of Jewels", "The War of the Ring" and "Sauron Defeated", but not included into LOTR. Antony Appleyard whose analysis of Black Speech was used for many Neo-BS dialects translated it as "Dush" = "Morgul" = "(dark) sorcery" and "goi" = "Minas" (tower, citadel, city with central tower)
2) "Morgul" in "Minas Morgul" is the compound word consisting of Sindarin "môr", "morn" (dark, black) < Etym. "MOR". It's believed that BS "bûrz" (dark) is derived from the same stem. In the list of names in "The Lost Road and the Other Writings" it's said that orcs of 1st Age translated name "Morgoth" as "Dark Lord" instead of Sindarin's "Black Foe"/"Black Enemy". However this translation was dismissed later. We can assume that 1st Age "Angband Orcish"/"Orquin" word "mor" was transformed into "bûrz" in CBS of Sauron in 2nd Age.
3) Dol Guldur is the Sindarin name of Sauron's stronghold in Mirkwood. This name translates as "Hill of Sorcery", where "guldur" means "(dark) sorcery", with further split-up into "gûl" + "dûr".
Sindarin "Gûl" is interesting word as it initially referred to "deep, secret knowledge", "wisdom", "art" and more specifically "magic". It is derived from the same stem "ÑGOL" (wise) as the name of Noldor elves (< "ÑGOLOD"). However it soon took negative tone and became refer to "evil, perverted knowledge, necromancy, sorcery". As the word "gûl" appeared in late 2nd Age in the name "Nazgûl" with BS meaning "phantom, shadow of dark magic, necromancy; slave, servant of Sauron", I suppose that it was also taken by 1st Age orcs first, to describe magic of their master.
Sindarin "dûr" means "dark, sombre" from Etymologies stem "DOƷ, DÔ"
4) Black Speech "dush" is belived to be borrowed from Valarin "dušamanûðân" as in "Aþâraphelûn Dušamanûðân" (Arda marred). Not denying this etymology, I propose, that additional source for it was the corruption of Sindarin "guldur" into "gûldush". As Black Speech and Orcish perverted not only the sounds of Sindarin, but the meaning of words too, as was shown above in translation of name Morgoth and word "gûl", it seems possible (at least for me) that "guldur" (lit. "sorcery-dark") transformed into "gûldush" (gûl-sorcery, sorcery to create Gûl). Probably "dush" got more practical, specific meaning for necromantic arts instead of global "marring" magic of Morgoth. Therefore addition of words "bûrz" or "mor" became unnecessary to translate "Morgul", so it became single-word "dush" in Black Speech instead of compound word of Sindarin.