Tiernan is a distinctive boys' name in United States, ranking #1872 in 2008 with 78 recorded births. The name reached its all-time peak in 2007 with 86 births ranking #1738. Since 1996, the popularity has increased by 358.8%. In 2008, approximately 1 in every 26,153 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.