Tiernan is a distinctive boys' name in United States, ranking #2397 in 2013 with 53 recorded births. The name reached its all-time peak in 2007 with 86 births ranking #1738. Since 1996, the popularity has increased by 211.8%. In 2013, approximately 1 in every 35,684 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.