E. Cobham Brewer 1810–1897. Dictionary of Phrase and Fable. 1898.
Sledge-hammer.
A sledge-hammer argument. A clincher; an argument which annihilates opposition at a blow. The sledge-hammer is the largest sort of hammer used by smiths, and is wielded by both hands. The word sledge is the Saxon slecge (a sledge).
