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

fafli

noun. bladder

A noun appearing as G. fafli “a bladder” in the Gnomish Lexicon of the 1910s, an elaboration of G. faf- “puff, blow” (GL/33).

Neo-Sindarin: I would adapt this word as ᴺS. faul “bladder” from ᴺS. faw- “puff, blow”, likely with the original sense “inflated thing”. This mirrors the etymology of English “bladder”, which is also derived from an ancient verb meaning “to blow”.