Webster's Revised Unabridged Dictionary · 1913

Deuce

Deuce (dūs) , noun

[French deux two, Old French deus, from Latin duo. See Two.]

1.
(Gaming) Two; a card or a die with two spots; as, the deuce of hearts.
2.
(Tennis) A condition of the score beginning whenever each side has won three strokes in the same game (also reckoned “40 all”), and reverted to as often as a tie is made until one of the sides secures two successive strokes following a tie or deuce, which decides the game.

Deuce , noun

[Compare Late Latin dusius, Armor, dus, teûz, phantom, specter; Gael. taibhs, taibhse, apparition, ghost; or from Old French deus God, from Latin deus (compare Deity).]

The devil; a demon. [Low]