ety>[ Written Mephostophilus in Shakespeare, Fletcher etc., Mephostophilis in Marlowe, but now generally Mephistopheles, as in Goethe: a made-up name, like most of the names of the medieval devils, but supposed by some to be formed (irregularly) from Gr. mh`, not, fw^s (fwt-), light, and fi`los, loving. ] A familiar spirit mentioned in the old legend of Sir John Faustus, and a principal agent in Marlowe's play Dr. Faustus and in Goethe's Faust. In medieval demonology, he was one of the seven chief devils. [ Century Dictionary 1906 ]

He is frequently referred to as “the Devil, ” but it was well understood that he was only a devil. Goethe took only the name and a few circumstances connected with the first appearance of Mephistopheles from the legend: the character, from first to last, is his own creation; and, in his own words, “on account of the irony and knowledge of the world it displays, is not easily comprehended.” Although he sometimes slyly used it (though less frequently than Faust) as a mask through which to speak with his own voice, he evidently drew the germ of some characteristics from his early associate, Merck. . . . The original form of this name was Mephostophiles. There has been much discussion in regard to its meaning, but Düntzen's conjecture is probably correct, -- that it was imperfectly formed by some one who knew little Greek, and was intended to signify “not loving the light.” B. Taylor, Notes to Faust. [ Century Dictionary 1906 ]

prop. a. Pertaining to, or resembling, the devil Mephistopheles, “a crafty, scoffing, relentless fiend;” devilish in character or aspect; crafty; showing cunning or ingenuity or wickedness; as, a mephistophelean glint in his eye.
Syn. -- devilish, diabolic, diabolical, mephistophelean. [ 1913 Webster ]