Sadako is a classical Japanese female given name written with the kanji characters 貞子, meaning chaste child, and ranks 72nd among traditional Japanese female given names. This name belongs to Japan's classical naming era when moral virtues were prominently featured in given names. The kanji tei refers to constancy, fidelity, and chastity, concepts that held significant cultural importance in traditional Japanese society, particularly regarding idealized feminine virtue and moral steadfastness.

The name developed during periods when Japanese naming conventions reflected Confucian values and Buddhist influences on social ethics. Throughout Japan's feudal and early modern periods, names incorporating concepts of virtue and proper conduct were especially popular for female children. The ko suffix, meaning child, became standardized in female naming during this classical era, creating a consistent pattern for names that would express parental aspirations for their daughters' character development and social standing.

Sadako is distinctive for its emphasis on constancy and moral integrity. The name carries formal and respectful connotations, suggesting dignity and unwavering principle. The character tei has historical connections to classical Chinese philosophy and Japanese ethical traditions, giving the name substantial cultural depth. This makes it more formal than many other traditional female names, appealing to families who valued classical education and philosophical grounding.

Sadako gained wider international recognition through popular culture, particularly the fictional character Sadako Yamamura from the Ring horror franchise, which became a global phenomenon. This association introduced the name to international audiences, though the name itself predates the modern fiction by decades. In Japan, the name maintains respect as a classical choice associated with virtue and principle. Women who carry this name continue to represent its traditional values, and it remains studied in Japanese onomastics and naming culture research. The name persists in both historical records and contemporary usage, representing an important link to classical Japanese ethical traditions.