If you do not find the Latin phrase you are looking for on this page, here are more Latin phrases about speech and communication:
In so many words.
Sesquipedalia verba (Horace)
Words that are a foot and half long; very long words.
verbis ad verbera
From words to blows.
nescit vox missa reverti
A word, once spoken, can never be recalled. (Horace)