Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!

Gnomish

suss

hush, sudden quiet; hush!

A noun for “hush, sudden quiet” in the Gnomish Lexicon of the 1910s, also used as an interjection “hush!” (GL/68). It may be related to later ᴹ√SLUS “whisper” from The Etymologies of the 1930s.