The Chinese word 疫苗 (yìmiáo) for "vaccine" is formed by combining two conceptual building blocks. The first character 疫 means "epidemic" or "pestilence", directly referencing the contagious disease. The second character 苗 means "seedling" or "sprout", but here it is used metaphorically to represent the seed or cultivated agent (historically, the cowpox matter) that is introduced into the body. Thus, the compound visually and conceptually represents the idea of a "disease seedling", a small, cultivated preparation used to inoculate against and sprout immunity against the epidemic disease.