Iain is a distinctive boys' name in United States, ranking #1181 in 2003 with 126 recorded births. The name reached its all-time peak in 2003 with 126 births ranking #1181. Since 1996, the popularity has increased by 46.5%. In 2003, approximately 1 in every 15,677 boys born was named Iain. FALLING Recent data shows the name is currently falling.