Katherleen is of English origin, derived from 'Catherine', which means 'pure'. It is a variant spelling of the name, adding an extra 'e' at the end. The name was popularized in medieval times through the veneration of Saint Catherine of Alexandria. Katherleen reached peak popularity in the United States during the mid-20th century.
The name Kathleen experienced peaks in popularity around the late teens to early twenties, with notable highs in 1917 (9 births), 1920 (13 births), and 1928 (10 births). However, it appears to have declined steadily thereafter, as indicated by the lower birth counts from the 1930s onwards. Despite this, Kathleen still maintained a consistent presence with an average of about 5-7 births per year from the 1940s to the late 1960s, totalling 200 births over the entire period.