Etymograph
>
Tolkien's Languages
>
Sindarin
>
Dictionary
>
thû
N
horrible darkness, black mist
Source:
PE17
:183,
https://eldamo.org/content/words/word-2950002373.html
originates from: CE
thūsē
"horrible darkness, black mist" (thūsē
>
tʰuːse
>
θuːse
>
θuːhe
>
θuːh
>
θuː
>
thú)