Kayin has been given to about 630 people in the United States since 1880. It was most common in 2005, which makes it a millennial-parent name.
Its best year was 2005, when 39 babies were given the name, ranking 3492nd. The typical living American called Kayin is about 19 years old today.
Source: US Social Security Administration, national and state name files, 2025 release, and the Office for National Statistics for England and Wales. Etymology researched and written by our editors. Living-population and median-age figures are our own estimates, described in the methodology.