There was once a boy who loves playing pranks.  Coincidentally, he lived near the woods. 

One of the pranks he played was to build a dam that prevented water from reaching the village via the stream that supplied the village.    After he build the dam, he ran to the village and told them that they saw a big monster drinking up all the water up stream and that the monster chased him but he managed to escape by hiding.  He also showed the cuts he received from his escape.    The story was believable because the water stopped for quite a while and continued (because a big storm broke the dam a few hours later and the water continued to flow).

Other times, he would kill some of the life stock from the village and make marks of some claws. 

Through a series of pranks, his story became more and more believable.  Finally, while he was creating another prank, he accidentally stepped on some insects and had an allergic reaction.  His feet swelled to many times its normal size and became very hot.  He ran to the stream to cool it down. 

The marks from his feet were discovered and that in term was the origin of the story of Big Foot in that village.