yahoo

A name given by Swift, in “Gulliver's Travels,” to a feigned race of brutes having the form of man and all his degrading passions.

[lowercase] A rough, brutal, uncouth character.

[lowercase] A greenhorn; a back-country lout.

One of a race of filthy brutes in Swift's “Gulliver's Travels.” See in the Dictionary of Noted Names in Fiction.

Hence, any brutish or vicious character.