Kaj is a distinctive boys' name in United States, ranking #12947 in 2025 with 5 recorded births. The name reached its all-time peak in 2006 with 20 births ranking #4599. Since 1996, the popularity has decreased by 61.5%. In 2025, approximately 1 in every 341,615 boys born was named Kaj. FALLING Recent data shows the name is currently falling.