A group of worms is called a clew. Collective nouns began as terms of hunting terminology in England and France in the 14th century. The popularity of the collective nouns inspired the use of light-hearted, humorous definitions of different animal groups often based on their traits or feelings they evoked.
A clew is defined as a ball of thread, yarn or cord. The term being coined as a collective noun for worms is a reflection of a group of worms resembling a clew of cord. Unusual terms used for a specific group of animals is linguistically referred to as terms of venery.