Gnomish
thim
noun. milk (after separation)
thimli
noun. whistle, piccolo
thimpa-
verb. to play a flute or whistle
thimp
noun. the stop on a flute
thimpion
noun. a piper
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!
A word appearing as G. thim “milk, after separation” in the Gnomish Lexicon of the 1910s, clearly related to the verb G. thin- “skim” (GL/71-72).
Neo-Sindarin: Although there are no other related words in Tolkien’s later writings, there are also no other alternatives for “milk” in the Sindarin language branch, so I would retain ᴺS. thim “milk” for purposes of Neo-Sindarin. I would use it especially for milk separated from cream. It might be derived from an ancient form such as ✱thimbē from a Neo-Root ✱ᴺ√THIM.