Final answer:
The request for fingernail clippings in a magical incantation represents sympathetic magic, specifically the law of contagion, suggesting a lingering magical link with the person to whom they belonged.
Step-by-step explanation:
The use of finger nail clippings of the intended victim in many magical incantations is an illustration of sympathetic magic, particularly the law of contagion. This concept posits that objects that were once in contact with a person continue to hold a magical connection to that individual. Therefore, personal items like nail clippings can be used in spells and rituals to influence or cause change in the victim's circumstances because they possess a part of that person's essence.
In the context of historical practices, this form of magic was seen across different cultures and manifested in rites such as curse tablets in ancient civilizations; these were employed to control or invoke supernatural forces for various purposes like love, justice, or success in competitions. Additionally, anthropologists have documented the use of performative language and material elements in both witchcraft and sorcery to accomplish desired outcomes.