Chickenpox, known medically as varicella, is a highly contagious disease caused by the varicella-zoster virus (VZV). The infection is characterized by a distinctive rash of small, intensely itchy blisters that typically appear first on the chest, back, and face before spreading. While usually a mild illness in childhood, the name itself is an unusual historical artifact whose origins are not fully certain. Understanding the name requires looking back several centuries when medical terminology was less precise and diseases were often named descriptively.
The Leading Theories on the “Chicken” Connection
One of the most widely accepted theories suggests the word “chicken” was added to the name to denote the disease’s relative mildness and insignificance. In historical English usage, the term “chicken” could imply something weak or trifling. Physician Samuel Johnson suggested that the designation came “from its being of no very great danger,” clearly contrasting it with other, more serious eruptive illnesses.
This theory posits that the name was a derogatory label, indicating that the ailment was a “chicken” or weak version of the much more severe disease, smallpox. The first documented use of the term “chicken pox” appeared in the mid-17th century, when this comparative naming convention was common. The superficial nature of the varicella lesions supported this idea, as they do not penetrate the deeper layers of the skin like the pustules of smallpox.
A second compelling theory focuses on the physical appearance of the characteristic skin lesions. The rash consists of small, fluid-filled vesicles that some observers believed resembled chickpeas, which derived their name from the Latin word cicer or the French term chiche pois. Another appearance-based hypothesis suggests the spots looked like the peck marks left on the skin by a chicken. Although the disease cannot be caught from poultry, this visual similarity may have been the source of the name.
Less-credited theories have also been proposed, including the idea that “chickenpox” is a corruption of the Old English term giccan pocca, which translates to “itching pustules.” Another suggestion is that “chicken” was a slang term for “child,” reflecting that the highly contagious virus primarily affected younger individuals. These theories highlight the historical difficulty in precisely naming diseases before the discovery of their specific viral causes.
Why the Disease Includes “Pox” in Its Name
The inclusion of “pox” in the name has a distinct historical context, as the word was used generally to describe any disease characterized by eruptive sores, blisters, or pustules. The term itself derives from the Old English word pocc, meaning a pustule or blister. Before the 16th century, numerous blistering illnesses were simply classified under the umbrella of “pox.”
This general term received further clarification with the emergence of severe diseases, leading to a system of comparative naming that solidified the use of “pox.” For instance, when syphilis arrived in Europe in the late 15th century, it was often called la grosse verole, or “the great pox,” to distinguish it from smallpox, which was then known as la petite verole, or “the small pox.” This established the convention of categorizing eruptive diseases by their severity and appearance.
The name “chickenpox” was therefore established to ensure a clear distinction from the devastating smallpox, which had a mortality rate of about 30%. In the 1600s, English physician Richard Morton misdiagnosed varicella as a milder form of smallpox, demonstrating the confusion of the time. It was not until 1767 that physician William Heberden published a detailed clinical description formally differentiating the two infections, noting that chickenpox lesions were superficial and non-fatal, unlike the deep, scarring pustules of smallpox.