People who do not consider things deeply often chatter or talk a lot.
2002, M. Scott Peck, The Road Less Traveled, 25th Anniversary Edition, →ISBN, page 156:
To the contrary, psychiatrists know well the truth of the old proverbs "Shallow brooks are noisy" and "Still waters run deep." We must not assume that someone whose feelings are modulated and controlled is not a passionate person.
1861, Reginald Neale Shutte, A Memoir of the Late Rev. Henry Newland, M.A, page 149:
Shallow brooks are noisy; deep waters are smooth. Depend upon it, when a man is deeply and strongly impressed with the truth of his own convictions, he is in no way tempted to rail at his neighbour.
2014, Student vs IAS T20: love is god and mercy divine, →ISBN:
My mother called me and asked, "Can you tell me the meaning of this, son. The deep river moves with silent majesty, but shallow brooks are noisy?"
