Neckam derived it from Dulia quasi sacrificium and carnis.

Skene justly observes that the triumph itself cannot be the point; but the word might get associated with the problem, either considered before its solution, puzzling to Pythagoras, or the demonstration, still difficult to us,—­a Pons Asinorum, like the 5th proposition.

Mr. Selden, in his preface to Drayton’s Polyolbion, says,—­

    “I cannot but digresse to admonition of abuse which this learned
    allusion, in his Troilus, by ignorance hath indured.

      “’I am till God mee better mind send,
      At Dulcarnon, right at my wit’s end.’

It’s not Neckam, or any else, that can make mee entertaine the least thought of the signification of Dulcarnon to be Pythagorus his sacrifice after his geometricall theorem in finding the square of an orthogonall triangle’s sides, or that it is a word of Latine deduction:  but, indeed, by easier pronunciation it was made of D’hulkarnyan[5], i.e. two-horned which the Mahometan Arabians {109} vie for a root in calculation, meaning Alexander, as that great dictator of knowledge, Joseph Scaliger (with some ancients) wills, but, by warranted opinion of my learned friend Mr. Lydyat, in his Emendatio Temporum, it began in Seleucus Nicanor, XII yeares after Alexander’s death.  The name was applyed, either because after time that Alexander had persuaded himself to be Jupiter Hammon’s sonne, whose statue was with Ram’s hornes, both his owne and his successors’ coins were stampt with horned images:  or else in respect of his II pillars erected in the East as a Nihil ultra[6] of his conquest, and some say because hee had in power the Easterne and Westerne World, signified in the two hornes.  But howsoever, it well fits the passage, either, as if hee had personated Creseide at the entrance of two wayes, not knowing which to take; in like sense as that of Prodicus his Hercules, Pythagoras his Y., or the Logicians Dilemma expresse; or else, which is the truth of his conceit, that hee was at a nonplus, as the interpretation in his next staffe makes plaine.  How many of noble Chaucer’s readers never so much as suspect this his short essay of knowledge, transcending the common Rode?  And by his treatise of the Astrolabe (which, I dare sweare, was chiefly learned out of Messahalah) it is plaine hee was much acquainted with the mathematiques, and amongst their authors had it.”

D’Herbelot says: 

“Dhoul (or Dhu) carnun, with the two horns, is the surname of Alexander, that is, of an ancient and fabulous Alexander of the first dynasty of the Persians. 795.  Article Sedd, Tagioug and Magioug. 993.  Article Khedher. 395. b. 335. b.  Fael.

    “But 317.  Escander, he says, Alexander the Great has the same
    title secondarily.  The truth probably is the reverse, that the
    fabulous personage was taken from the real conqueror.