words _Bog z’milui_, signifying ‘God have mercy,’ an etymology which fits in with that peculiar devotion to prayer which was characteristic of the Bogomilian religion, which harmonizes with that of the allied sectaries, the Massalians and Euchites, and which would be still intelligible to all Sclavonic peoples, from the White Sea to the Ægean. We need not, however, go so far as to deny that the Bogomilian heresy took its characteristic shape under the direction of a Bulgarian heresiarch. The historic existence of the first Bogomilian pope seems sufficiently attested,[16] but the Bulgarian traditions name him indifferently Jeremias and Bogomil, and it is quite possible that the latter name was added at a later time by a confusion with the Sclavonic homonym for Massalians and Euchites. Through all the varying phases of Bulgarian history the Bogomiles, as these Sclavonic Manichæans are now known, hold their own. It seems certain that the Bulgarian Czars, in their struggle with Byzantium, did not wish to alienate a powerful party at home, and we hear occasionally ominous whispers that Bulgarian Emperors themselves leaned towards the doctrine of the Two Principles.[17] The Bulgarian heresy was perpetually fed from its Oriental sources by new Byzantine transplantations, and in the tenth century the Emperor John Zimisces did much for the propagation of Gnosticism among the Sclaves by transporting a more powerful colony of Armenians than any that had gone before ‘from the Chalybian hills to the valleys of Mount Hæmus.’ It is now that the Bogomilian heresy begins to spread beyond the limits of Bulgaria, among the kindred Serbian tribes to the west. Bulgaria, earlier civilized from her closer contact with Byzantium, was exercising during these centuries a predominating influence over the less cultured Serbs. From the Bulgarian missionaries Serbia first received the seeds of her orthodox Christianity, and there can be no doubt that proselytism was at work on the Manichæan side as well. Add to this that a large part of Serbia fell at different times under the Bulgarian dominion. By the end of the tenth century the Bogomiles have taken firm root among the Serbs. In the legend of the Serbian prince, St. Vladimir,[18] one of his highest merits is that he was the zealous enemy of the Bogomiles. St. Vladimir certainly included in his dominions parts of what is now the Herzegovina, and, according to some accounts, Bosnia as well.