I did a mock case in school on copyright infringement. It may help. Skip down to the last paragraph for conclusion. Here it is:
Today, we will decide whether the defendants are guilty or innocent of copyright infringement.
The defendant is guilty. The United States Copyright Act of 1976 prohibits anyone from copying the original artistic work of another, without permission. If anyone uses a part of a another’s work, even a very small part, like the one note that the defendant used, without the copyright owner’s consent, he is still infringing the owner’s rights. The maximum criminal penalty for copyright infringement is five years in prison and $250,000 in fines.
Also in Folsom v. Marsh, 9 F. Cas. 342,348 (No. 4,901)(CCD Mass. 1841) the court ruled that ”... look to the nature and objects of the selections made, the quantity and value of the materials used, and the degree in which the use may prejudice the sale, or diminish the profits, or supersede the objects, of the original work.”
In Bridgeport v. Comb they ruled that “The exclusive right of the owner of copyright in a sound recording under clause (2) of section 106 is limited to the right to prepare a derivative work in which the actual sounds fixed in the sound recording are rearranged, remixed, or otherwise altered in sequence or quality.”
Those laws are only useful for significant similarities between a derivative and an original creation. The one note sample can be common in many different tracks. If it is, then the plaintiff has no right to hold copyright over the sample or require permission to use it.
In Emmerson v. Davies, 8 F. Cas. 615 (No. 4,436)(CCD Mass. 1845) the court ruled that ”... in truth, in literature, in science and in art, there are, and can be, few, if any, things, which in an abstract sense, are strictly new and original throughout. Every book in literature, science and art, borrows, and must necessarily borrow, and use much which was well known and used before.“
*The United States Copyright Act of 1976 states that copyrights are only for “The designer or other owner of an original design of a useful article which makes the article attractive or distinctive ”. *
Copyright can only be claimed if distinctive, therefore I would say yes to your first question. Considering Harry Potter is a worldwide franchise and very popular, the name is very distinctive and any use of the name would violate copyright law. To your second question, it wouldn’t be a problem as long a you do what Seek_Kolinahr said.
Hope this helps.