Webster's Revised Unabridged Dictionary · 1913

fiend

fiend (fēnd) , noun

[Old English fend, find, fiend, feond, fiend, foe, Anglo-Saxon feónd; akin to Old Saxon fīond, Dutch vijand enemy, Old High German fīant, German feind, Icelandic fjānd, Swedish & Danish fiende, Gothic fijands; orig. present participle of a verb meaning to hate, Anglo-Saxon feón, feógan, Old High German fī{not transcribed}n, Gothic fijan, Sanskrit pīy to scorn; prob. akin to English feud a quarrel. r81. Compare Foe, Friend.]

An implacable or malicious foe; one who is diabolically wicked or cruel; an infernal being; -- applied specifically to the devil or a demon.
Into this wild abyss the wary fiend Stood on the brink of Hell and looked a while. — Milton
O woman! woman! when to ill thy mind Is bent, all hell contains no fouler fiend. — Pope