ringworm

The word "ringworm" is a classic example of a descriptive folk etymology. It is a compound formed from two Old English words: 'hring' (ring) and 'wyrm' (worm). The name originates from the pre-modern medical belief that the circular, spreading lesions characteristic of the fungal infection were caused by a small, burrowing worm beneath the skin. While modern science has identified the true cause as various dermatophyte fungi, the vivid, descriptive name has persisted in the language. Thus, the term's logic is based on the literal, observable symptom (a ring-shaped mark) combined with an antiquated theory of its cause (a worm).

Structure: ring + worm ring: Old English origin, meaning a circular band or shape. In this compound, it describes the characteristic circular appearance of the rash. worm: Old English origin, referring to a creeping or parasitic animal. In this compound, it reflects the archaic belief that the infection was caused by a parasitic worm under the skin.