Ok just to let you know I play Pokemon y and I bred female and male charizard and they both knew inferno
"If both parents know a move that the child would learn by level up, the child will also know it upon hatching."
Since Charmander can learn inferno by level up and both parents knew it, inferno was passed on to the Charmander egg
Source & more info
Well... It's probably just passed down from the parent because my Umbreon that knew shadow ball had eevees that knew shadow ball(and shadow ball is not an egg move, I can tell you that)