The core of the Proto-Runo Song of Killing a Snake was formed from an unknown oral source which transmitted to the runo song singers an Apocrypha of Stug-Christ killing Snake-Devil. The Apocrypha was mainly based on the High-Old-German version of the Physiologus. Later on, another apocryphal theme widespread in the medieval Europe was added to the proto song: small plants growing from Christ's blood, or Virgin Mary's milk or tears. As the consequence of the introduction of this theme into the proto song, there was gradually formed a theme of a snake from whose milk, blood, or tears grow(s) trees or an oak, or the milk milked from the snake by Virgin Mary was seen as an ointment for healing wounds. By turning of the (proto) song into an incantation against wounds, the motif of killing a snake started falling into oblivion.