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!

Qenya 

lusse

noun. whispering sound

A noun appearing as ᴹQ. lusse “a whispering sound” in The Etymologies of the 1930s based on the root ᴹ√SLUS of similar meaning (Ety/SLUS).

Neo-Quenya: For purposes of Neo-Quenya I would updates this to ᴺQ. hlussë since initial sl became voiceless hl in Quenya.