E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A broken reed. Something not to be trusted for support. Egypt is called a broken reed, to which Hezekiah, could not trust if the Assyrians made war on Jorusalem, which broken reed if a man leans on, it will go into his hand and pierce it. Reed walking sticks are referred to.
A bruised reed, in Bible language, means a believer weak in grace. A bruised reed [God] will not break.