Webster's Revised Unabridged Dictionary · 1913

Fallacy

Fallacy (fal"lȧ*sy) , noun

[Old English fallace, fallas, deception, French fallace, from Latin fallacia, from fallax deceitful, deceptive, from fallere to deceive. See Fail.]

1.
Deceptive or false appearance; deceitfulness; that which misleads the eye or the mind; deception.
Winning by conquest what the first man lost, By fallacy surprised. — Milton
2.
(Logic) An argument, or apparent argument, which professes to be decisive of the matter at issue, while in reality it is not; a sophism.