broken reed

From broken + reed (with reference to the quotation in 1611, see below).

• "Lo, thou trustest in the staff of this broken reed, on Egypt; whereon if a man lean, it will go into his hand, and pierce it: so is Pharaoh king of Egypt to all that trust in him."
• "Many of the big estates survived. Nor was the peasantry a broken reed in terms of demand for manufactured products."
• "A law on privacy would be cumbersome and hard to police, but as the Press Complaints Commission is a broken reed in this matter, each scandal makes it harder to stave off calls for legislation."

• slender reed