Cognomen Kajn (Kajn 
) , around the globe, is a very rare surname. The family name Kajn is habitual in Croatia, where it is a rare surname, the United Kingdom, where it is an extremely rare surname, and Canada. Not in comparison with a country's population, it is commonest in India, Croatia, and the United Kingdom. Also, Kajn is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Kajn | Canada, United States, United Kingdom, India, Croatia |