Middle Primitive Elvish
gos
root. dread
arʒā
noun/adjective. dread
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
A root in The Etymologies of the 1930s glossed “dread” with two variations: ᴹ√GOS and ᴹ√GOTH (Ety/GOS). It was an element in quite a few names in Silmarillion drafts from the 1930s, such as ᴹQ. Mandos “Dread Imprisoner” (Ety/MBAD), ᴹQ. Osse (Ety/GOS), N. Gothmog (Ety/MBAW), N. Tauros “Forest-Dread” (Ety/TÁWAR), and N. Dor-Daideloth “Land of the Shadow of Dread” (LR/405), the last of these containing N. deloth “abhorrence, detestation, loathing” = ᴹ√DYEL + ᴹ√GOTH (Ety/DYEL).
In Tolkien’s later writings, many of these names were given new forms or etymologies: Q. Mandos “Castle of Custody” = mando + osto (MR/350); Q. Ossë as an adaptation of his Valarin name Oš(o)šai (WJ/400); S. Tauron “Forester” (PM/358). This calls into question whether ᴹ√GOS or ᴹ√GOTH survived as a root. It does have a few useful derivatives for the purposes of Neo-Eldarin, however, such as N. gosta- “fear exceedingly”.