It is highly unlikely that J. K. Rowling copied the name of Harry Potter from the protagonist of the 1986 movie Troll. Although they both have the same name, it is not necessarily uncommon for two people to have the same name. Furthermore, it is absurd to assume that J. K. Rowling would require to copy the name of her novel's protagonist from a random movie and then lie about it. She has also told in several interviews that Harry Potter's name was taken from her childhood friend Ian Potter and her favorite boy's name "Harry".