A video has emerged from the US of a toddler's hilarious reaction to seeing a rattle snake in the back garden of his parent's house.

The footage, captured on May 18 at a home in Payne County, OK, shows the little boy observing the reptile through a glass door and calling it a 'dragon' to the amusement of his parents.

''One evening after a rainstorm, this snake came from the woods behind my house looking for a dry spot to hangout,'' the filmer later wrote online.

''My son's favorite bedtime book is called 'Dragons love tacos', that may be the reason he keeps calling the snake a 'dragon' or a 'crocodile','' he added.