PETAR.  A Slavic form of Peter (q.v.), meaning "a stone." (Standard Croatian-English and English-Croatian Dictionary, Bogadek, 1917).  Usage: Bulgaria (Петър), Croatia, Serbia (Пeтap), Yugoslavia (Пeтap).

... He walks along the tiny path below the overhanging cliff; for the Ribnica lies in a deep cutting, and not another word does he vouchsafe till, with a hoarse whisper, he answers a crisp challenge.  Then other figures rise from the surrounding boulders.  All the men I know, and silently they push forward and grasp me by the hand in welcome.  Then Petar takes me to another cave smaller than the last, and with a natural parapet, over which I clamber.  Once inside I see that no bullet can penetrate here, and smile at the thoughtfulness of these men... (Blackwood's Edinburgh Magazine, v.173,  1903)