Pet form of Katherine, from Greek 'katharos' meaning pure.
Kitty began as a medieval pet form of Katherine, itself derived from the Greek Aikaterine — a name whose precise etymology has sparked centuries of debate, with scholars proposing roots ranging from the Greek katharos (pure) to an ancient Coptic name. Through the soft consonant shift common in English diminutives, Catherine became Kate, and Kate softened further into Kitty, following the same path by which William becomes Will becomes Billy. For centuries it was understood as an affectionate nickname rather than a name in its own right, worn lightly by kitchen maids and countesses alike.
Literature gave Kitty some of its most enduring portraits. Tolstoy's Princess Kitty Shcherbatskaya in Anna Karenina is one of the great romantic heroines of the nineteenth century — young, guileless, devastated by Vronsky and ultimately redeemed by Levin's steadfast love. Jane Austen peopled her novels with Kittys too, most memorably the flighty Kitty Bennet in Pride and Prejudice, whose giggling contrasts sharply with Elizabeth's wit.
These literary associations gave Kitty a reputation for warmth and vivacity, occasionally shading into frivolity. By the mid-twentieth century, Kitty had largely receded as a standalone choice, overshadowed by the more formal Katherine and the sharper Kate. But its very quaintness has made it attractive again to parents drawn to names with Victorian softness and genuine historical depth. Kitty carries the rare quality of feeling simultaneously old-fashioned and entirely wearable, a diminutive that grew up without losing its charm.