E. Cobham Brewer 1810–1897. Dictionary of Phrase and Fable. 1898.
Dead Set.
He made a dead set at her. A pointed or decided determination to bring matters to a crisis. The allusion is to a setter dog that has discovered game, and makes a dead set at it.
1
To be at a dead set is to be set fast, so as not to be able to move. The allusion is to machinery.
2
To make a dead set upon someone is to attack him resolutely, to set upon him; the allusion being to dogs, bulls, etc., set on each other to fight.
