The name Karen is a variant of the ancient Greek name Katerina, which is derived from the Greek word "katharos," meaning "pure" or "clear." It is believed to have originated in the Mediterranean region during the Byzantine era.

In ancient Greece, the name Katerina was associated with the Greek goddess Hecate, who was revered as the goddess of witchcraft, sorcery, and the night. The name was popular among early Christian communities in the region, and it gained wider recognition after the rise of Christianity.

One of the earliest recorded instances of the name Karen can be found in the hagiographies (biographies of saints) of the 5th century. St. Karen, also known as St. Cyrene, was a martyr from Tyre (modern-day Lebanon) who was persecuted for her Christian faith during the reign of the Roman Emperor Diocletian in the early 4th century.

In the Middle Ages, the name Karen gained popularity across Europe, particularly in Scandinavia and the British Isles. Notable historical figures with the name Karen include Karen Brahes (1528-1604), a Danish noblewoman and astronomer who made significant contributions to the scientific understanding of the Tychonic system of planetary motion.

During the Renaissance, the name Karen was associated with the arts and literature. Karen Anckers (1493-1532) was a Dutch Renaissance poet and writer who is considered one of the earliest female authors in the Netherlands. Karen von Lilienfeld (1520-1589) was an Austrian Renaissance composer and musician who wrote sacred and secular works.

In more recent history, Karen Blixen (1885-1962), a Danish author and baroness, gained international acclaim for her memoir "Out of Africa," which recounted her experiences as a plantation owner in colonial Kenya.

Karen Horney (1885-1952) was a German-American psychoanalyst who made significant contributions to the field of psychoanalytic theory and is considered one of the founders of modern feminist psychology.