That was my sheet anchor—i.e. my best hope, my last
refuge. The sheet anchor is the largest anchor of a ship, which, in
stress of weather, is the sailor's chief dependence. The word
sheet is a corruption of the word
shote (thrown out), meaning the anchor
“thrown out” in foul weather. The Greeks and Romans said,
“my sacred anchor,” because the
sheet anchor was always dedicated to some god.
The Anchor, in Christian art, is given to
Clement of Rome and Nicolas of Bari. Pope Clement, in A.D. 80, was
bound to an anchor and cast into the sea. Nicolas of Bari is the
patron saint of sailors.
The anchor is apeak, that is, the cable
of the anchor is so tight that the ship is drawn completely over
it. (See Bower Anchor, Sheet Anchor.)
The Anchor comes home, the anchor has been
dragged from its hold. Figuratively, the enterprise has failed,
notwithstanding the precautions employed.
To weigh anchor to haul in the anchor, that the
ship may sail away from its mooring. Figuratively, to begin an
enterprise which has hung on hand.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894